Qongancjuinity in ]Y[arriacje, 
by 
E. S. McKee, M. D., 
Cincinnati. CONSANGUINITY IN MARRIAGE. 
BV K. H. M(KEK, M. D., CINCINNATI. 
We find, permeating all classes of all nations, 
the belief that consanguineous marriages are fol- 
lowed by evil effects upon the offspring. This 
tradition pains credence from occasional cases 
where dire results have occurred, and the post hoc 
is taken for the propter hoc, the many instances 
where no evil happened being forgotten. 
An endeavor to show the falsity of this belief 
is the object of this paper. 
Attention will be directed, in the greater part, 
to the marriage of cousins, especially those of the 
first degree. (This is partially because the major- 
ity of consanguineous marriages are between 
cousins, and because the marriage of relatives 
nearer than first cousins, even if proven not to he 
harmful to the offspring, should he discouraged on 
other grounds.) 
Consanguinity denotes blood relationship. It 
is quite different from affinity, which signifies re- 
lationship by marriage. A man is related to his 
brother by consanguinity. His wife is related to 
that brother by affinity. 
Lineal consanguinity is that which exists be- 
tween persons in the direct line of descent or 2 
CONSANGUINITY IN MARRIAGE. 
ascent. The is collateral when two 
persons descend from a common ancestor, but not 
one from the other. 
Great confusion has arisen from counting de- 
grees of consanguinity by two different methods. 
Civil law counts the number of generations up 
from the one individual to the common ancestor, 
then down to the other. The canonical law 
counts the degrees in but one line, the longer, 
from the common ancestor. The canon law, for- 
mulated by Pope Gregory I., A. D. 590-604, is 
imperfect. It gives persons the same relationship 
to a certain person when it is not true. Prohibiting 
marriage in the third degree by' the canon law 
prohibits many more than by the civil law. 
The relationship existing between Jupiter and 
Juno, Osiris and Isis, shows that unions of the 
closest degrees of consanguinity were not ab- 
horred in ancient mythologies. The story of 
Edipus and Jocastra shows that marriage in the 
direct line of descent was looked upon as impious. 
The ancient Egyptians intermarried very closely, 
a large proportion being between brother and sister. 
The Persians did likewise, as did also the Israel- 
ites prior to Moses. Abraham married his half- 
sister, Sarah; Isaac his first-cousin, Rebekah, and 
Jacob his two first-cousins, Rachel and Leah. 
This was a nation renowned for vigor, and in the 
first fourteen generations reached six hundred 
thousand fighting men. The sons of Adam must 
have married their sisters, and we are all descend- 
ants from consanguineous marriages, and, accord- 
ing to some, idiots. 
The Mosaic law, Leviticus xviii., prohibits 
the following marriages: With a parent, step- 
mother, sister, half-sister, grand-daughter, aunt or 
uncle’s \yife, step-daughter or step-grand-daughter, E. 8. m’kKE, M. I). 
3 
or with a wife’s sister during the lifetime of the 
former. 
The Greeks forbade marriage in the direct line 
of descent, yet permitted it between half-brother 
and half-sister. The Athenians allowed marriage 
between brother and sister of the same hither, but 
not of the same mother. The Lacedemonians 
allowed marriage between uterine brothers and 
sisters, hut not between those having the same 
father and mother. 
The Romans excluded marriage between 
brothers and sisters, whole or half, and any mar- 
riages nearer in degree than first-cousins were 
practically illegal. The institutes of Justinian 
forbade marriage in direct line and in collateral 
line within the fourth degree. First-cousins and 
all remoter kin might marry. 
The present canon law, in force in most Roman 
Catholic countries, forbids marriage only inside 
of the fourth degree, that is, third-cousins are for- 
bidden to marry. The civil law allows the first 
civil degree, that is, first cousins, to marry. 
Henry VIII. modified very stringent marriage 
laws in England. They are now practically the 
Levitical. First-cousins may marry, also nephew 
and great-aunt, niece and great-uncle. While a 
man may not marry his grand-mother, he may his 
sister. This law holds in Great Britain, Ireland, 
and the colonies. The law forbidding a man to 
marry his deceased wife’s sister is not Levitical, 
and, despite the annual effort to throw it off, re- 
mains in the home country, hut has been dis- 
pensed with in Canada and Australia. 
The Levitical code is followed generally in the 
various States of this nation, hut New Hampshire, 
Ohio, and Indiana forbid the marriage of first- 4 
CONSANGUINITY IN MARRIAGE. 
cousins. Most States forbid a man to marry his 
aunt or niece, but it is permissible in New York. 
Reliable statistics, free from flaws, are exceed- 
ingly difficult to procure. The best we can do is 
to gather all the reliable testimony obtainable. 
George H. Darwin, who has so thoroughly 
studied the marriages between first-cousins in 
England, says: “It thus appears that in London, 
comprising all classes, the cousin marriages are 
about per cent.; in urban districts, 2 per cent.; 
in rural districts, 2J per cent.; among the landed 
gentry, 3J per cent.; aristocracy, 4J per cent. An 
average for England of 3 per cent. The average 
for Scotland is 5] per cent. This large percentage 
leads Mr. Darwin to think that such marriages 
are more frequent in Scotland than in England 
and Wales. From the mountainous nature of the 
country this is, perhaps, to be expected. After a 
thorough search through the institutions for idiots, 
insane, deaf and dumb, etc., he found that be- 
tween 3 and 4 per cent, of these descended from 
consanguineous marriages. In 306 families, in 
the urban districts other than London, concerning 
which accurate information could be obtained, 8 
— that is to say nearly 2.2 per cent. — were the 
offspring of first-cousins. From his investiga- 
tions Mr. Darwin had deduced 2 per cent, as the 
proportion of first-cousin marriages in these dis- 
tricts. Including 350 cases from Newcastle, con- 
cerning which the information is not so accurate, 
reduces this to 1.9 per cent. Probably 3 or 4 per 
cent, of the patients in the idiot and lunatic 
asylums are the offspring of first-cousins. Taking 
into consideration the inaccuracies of the modes 
of gaining information, both as to the number of 
these descending from consanguineous marriages 
and the percentage of these marriages — 3 per e. s. m'kke, m. d. 
5 
cent. — the above can not be said to be in excess. 
As to deaf-mutes, the proportion of offspring of 
first-cousin marriages is precisely the same as the 
proportion of such marriages to the whole number 
of marriages. Therefore there is no evidence 
whatever of any ill-results accruing to the off- 
spring from the cousinship of their parents. 
Professor Mantagazza, M. Boudin, and Dr. 
Bailey are of the opinion that consanguinity tends 
to sterility. After a most thorough investigation, 
making much use of Burke’s “ Landed Gentry,” 
and “ Peerage,” Darwin finds that consanguineous 
marriages are slightly more fertile than the non- 
consanguineous. He thinks the cause of this is 
probably the fact that marriages between first- 
cousins will be more apt to take place where there 
is a large group of persons who bear that relation- 
ship to each other. In such families fertility will 
he hereditary. The alleged infertility of consan- 
guineous marriages, whether direct or indirect, 
can not be substantiated. Mr. Darwin’s investi- 
gations concerning the alleged death rate among 
the offspring of cousins, although rather meagre 
and unsatisfactory, tend to invalidate the allega- 
tion, yet there remains a shade of evidence that 
the death rate is slightly higher than among the 
families of non-consanguineous parents. 
Dr. Crichton-Browne, of the West Riding 
Lunatic Asylum, England, says: “ It has always 
seemed to me that the great danger attending 
such marriages consists in the intensification of 
the morbid constitutional tendencies which they 
favor. Hereditary diseases and cachexia are 
much more likely to be shared by cousins than by 
persons who are in no way related, and these are 
transmitted with more than double intensity when 6 
CONSANGUINITY IN MARRIAGE. 
common to both parents. Persons of similar 
temperaments ought not to marry.” 
Dr. Howden, of Montrose Lunatic Asylum, 
Scotland, says: “As regards insanity, my own 
opinion is, that unless there exists an hereditary 
predisposition, the marriage of cousins has no 
effect in producing it. * * * Neither in in- 
sanity, nor in any other abnormal propensity, do 
two plus two produce four; there is always another 
factor at work, neutralizing intensification and 
bringing things back to the normal.” 
Dr. Lauder Lindsay, Murray Royal Institution 
for the Insane, Perth, Scotland, is of the opinion 
that the ill effects of cousin marriages are much 
less, in regard to insanity, than represented. 
Dr. Scott, of Exeter, says that 7 out of 241 
families in which deaf and dumb children have 
been born were first-cousin marriages. In three 
or four of these families more than one child was 
so afflicted. 
Dr. Arthur Hopper, of the Deaf and Dumb 
School at Birmingham, out of sixty-two congeni- 
tally deaf children, found not one to be the off- 
spring of consanguineous marriages. He thinks 
it possible for deafness to show itself in future 
generations, though dormant now. 
Mr. Neill, of the Northern Counties Institu- 
tion, Newcastle-on-the-Tyne, says: “Three hun- 
dred and fifty have been admitted into the 
institution, and I think in not more than six cases 
were the parents cousins. In one family, whose 
parents were cousins, there were four deaf-mutes.” 
Mr. Neill has been engaged in the tuition of the 
deaf and dumb for more than forty years. He 
thinks the offspring of cousins so affected fewer 
than supposed. E. 8. m'kEH, M. D. 
7 
Mr. I )avid Buxton, of Liverpool, thinks that 
one in ten of tlie deaf and dumb in his school 
descend from consanguineous marriages. 
Mr. William Sleight, of the Brighton School, 
says: “As far as I have been able to ascertain, 
about 7 per cent, of the congenitally deaf children 
are the offspring of cousins.” 
Dr. George Wallington Grabham, Asylum for 
Idiots, Earleswood, says: “Consanguinity of 
parents accounts (partially only) for about 0 per 
cent, of the cases which have been admitted into 
the asylum during the last six years and a half, 
lull cases only out of 543, the parents were first- 
cousins, and no other cause could he obtained. 
Where hereditary predisposition coexists with 
marriage of consanguinity, we frequently find, as 
might be expected, more than one child affected. 
We may, therefore, regard with less disfavor mar- 
riages between cousins where there is no heredi- 
tary taint on either side.” 
Dr. Rayner, of the Hanwell Lunatic Asylum, 
reports 3 out of 255 as the offspring of cousins; 
Dr. Bvewater Ward, of the Warneford, Oxford, 
Lunatic Asylum, none out of 20; Dr. Adam, 
Metropolitan District, Caterham, lunatics, 20 out 
of 500; Dr. Yellowless, Glamorgan County, luna- 
tics, 9 out of 218; Dr. Lawrence, Chester County, 
lunatics, 3 out of 225; Dr. Mickle, Grove Hail, 
Bow, 8 out of 181; Dr. Oscar Woods, Hatton, 
Warwick, 8 out of 258; Dr. Grabham, Earleswood, 
Surrey, idiots, 53 out of 1,388; Dr. Orange, Broad- 
moore, lunatics, 2 out of 150; Dr. Gilchrist, Crich- 
ton Royal Institution, Dumfries, 4 out of 51; Dr. 
Anderson, Southern Counties, Dumfries, 8 out of 
200; Dr. McIntosh, Perth District, Murthlv, 3 out 
of 78; Mr. W. H. Warwick, Asylum for tlie Deaf 
and Dumb, Kent, 52 out of 032. 8 
CONSANGUINITY IN MARKIAGK. 
Dr. Arthur Mitchell, of Edinburgh, Depart- 
ment Commissioner of Lunacy in Scotland, has 
made a most thorough investigation of the sub- 
ject in his paper, “Blood Relation in Marriage.” 
(He found among 146 born from 45 consanguine- 
ous marriages, 37 of them being fertile, 5.5 per 
cent, idiots, 3.4 per cent, imbecile, 7.5 per cent, 
insane, 1.4 per cent, epileptic, 3 per cent, paralytic, 
1.4 per cent, deaf-mutes, 2 per cent, blind, 15 per 
cent, consumptive, scrofulous, or manifestly weak 
in constitution.) He arrives at the following con- 
clusion: Under favorable conditions of life the 
apparent ill effects were frequently almost nil; 
while if the children are underfed, badly housed 
and clothed, the evil might become very marked. 
He thinks the danger greater between uterine 
relatives than those having a common father, but 
different mothers, for two reasons: One because 
more good or evil is inherited from the mother; the 
other because, while we are always the sons of our 
mothers, yet we may not be the sons of our fathers. 
Sir W. Wilde, in his appendix to “Aural Sur- 
gery,” considers consanguinity of parents as a 
paramount cause of ear troubles in children. 
Mayr found the following proportions of deaf 
and dumb, out of 10,000 persons, in various coun- 
tries: In the Netherlands, 6.72; among Netherland 
Jews, 15.34; in Germany, 19.32; among Bavarian 
Jews, 36.47; in Baden, 24.24; in Prussia, 12.44. 
Reich found deaf and dumb, out of 10,000 
persons, as follows: Argentine Republic, 75.74; 
United States of North America, 8.39; British 
Australia, 5.65. He lays this to the fact that in the 
Argentine Republic the people are enervated and 
passive. In both other lands they are very active. 
In Sweden consanguineous marriages are not 
more numerous than in North America, yet, from E. S. M KEE, M. I). 
9 
the abuse of alcohol and other habits detrimental 
to the general system, the frequency of the deaf 
and dumb is 20.57 to 10,000 inhabitants. Falk 
also considers the social condition one of the 
weightiest tendencies to deafness and dumbness. 
Boudin and others claim that the greater fre- 
quency of mental diseases among earls and the 
aristocracy is due to consanguineous marriages. 
It is probable that this is not so much more fre- 
quent among them than among other people, but 
it is more noticed. Then, too, why not lay it to 
debauchery, extravagance, and corruption? 
I>r. Charles F. Withington, of Roxbury, Mass., 
read a paper before the Massachusetts Medical 
Society in 1885, in which he gave a collection of 
108 consanguineous marriages; 103 were fertile, 
bearing 413 children. Excluding all those having 
defects of the slightest nature, 312 remained, being 
75.5 per cent. This is as high a percentage, cer- 
tainly, as can he found in any equal number of 
children taken at random. The defects present 
could not he ascribed positively to the consanguin- 
ity of the parents. They consisted of: Deaf-mutes, 
12; insane, 7; idiots, 13; blind, 8; died of con- 
sumption, 15; nervous, 5; of less than average intel- 
ligence, 8; died in infancy, 16; not robust, 6; her- 
maphrodite, 1; died of meningitis, 2; cross-eyed, 
2; still-born, 2; deaf(noteongenital). 2; stammerers, 
2; myopic, 2; deformed, 2; epileptic, 1; total, 101. 
Of these 108 marriages fertility was present in 
all save 5. In one of these there was a mechan- 
ical impediment on the part of the wife; in another 
the marriage had lasted only two years. Three of 
these were physicians, and one a member of the 
Boston Tea rarty, certainly very respectable mem- 
bers of Society. 
The marriage of Jones and Jones, Brown and 10 
CONSANGUINITY IN MARRIAGE. 
Brown, Smith and Smith, probably means the 
marriage of distant relatives, though the parties 
themselves are not aware of it. 
Dr. Bemis reported to the American Medical 
Association a collection of 843 consanguineous 
marriages, producing 3,942 children, 4.6 births per 
marriage; 28.7 per cent, are put down as defective; 
3.6 per cent, as deaf-mutes; 2.1 per cent, as blind; 
7 per cent, as idiots; 2.04 per cent, as insane; 1.5 
per cent, as epileptic; 7.6 per cent, as scrofulous, 
and 2.4 per cent, as deformed; 22.4 per cent, are 
recorded as having died young. 
M. Burgeois gives the history of his own fam- 
ily, descended from a consanguineous union in the 
seventeenth century. Sixty-eight marriages all 
feel the effects of consanguinity, yet only one was 
infertile, and this the fault of the wife, a woman 
of alien stock. The health of all the 200 descend- 
ants is excellent, except in one family, where 
scrofula has crept in. 
Seguin gives the particulars of ten marriages 
of kin in his own family, two of the number 
being uncle with niece, and the rest of first- 
cousins. Sixty-one children were born, not one of 
whom showed deaf-mutism, hydrocephalus, stam- 
mering, or polydactylism. All lived to be grown up. 
Dally gives a case of intermarriage between 
two families, all being first-cousins, save two, who 
were second-cousins. This has continued for five 
generations, with an average of three or four chil- 
dren per marriage. There has been no case of 
idiocy or deaf-mutism, and but one of insanity, in 
an old woman. 
M. Voisan reports observations, in the isolated 
commune of Batz, of 46 consanguineous marriages. 
These gave 172 children. Sterility occurred in 
two instances. Mental disorders, idiocy, deaf- k. s. m'kkk, m. d. 
11 
mutism, hemeralopia, alhinoism, retinitis pigmen- 
tosa, or malformations, were all unknown. The 
community consisted of 3,300 souls. They were 
simple, intelligent, and moral, and had intermar- 
ried from time immemorial. 
Dr. Cameron makes the statement, based upon 
the Irish census of 18<S1, that of the 5,130 deaf- 
mutes enumerated in the country, 135, or ‘2.0 per 
cent, were the children of first-cousins. 
Dr. Derby, in a total of 12,130 cases in his 
ophthalmic practice, has met 23 cases of retinitis 
pigmentosa. Ten of these were the children of 
cousins. In none of the 23 cases were any other 
abnormalities noted. Dr. Derby also gives figures 
by other observers, which, together with his own 
just referred to, amount to 210 cases. In 70 there 
was relationship, in 139 no relationship, in 1 no 
information. 
Dr. Standish, in the Carney Hospital, Boston, 
in a total of 3,720 patients, found 3 cases of 
retinitis pigmentosa. In 1 there was no record as 
to consanguinity, in 1 no relationship, in 1 the 
parents were first cousins. 
Liebreich found retinitis pigmentosa and deaf- 
mutism closely connected. From investigations 
with the ophthalmoscope among the inhabitants 
of Berlin, he found deaf-mutism among the 
('atholics, who prohibit consanguineous marriages, 
1 in 3,(MX); among Protestants, who permit, 1 in 
2,(MM); among the Jews, who encourage, 1 in 4(M). 
According to Liebreich and data from Moorfields 
Hospital, the development of retinitis pigmentosa 
is favored by consanguineous marriages. 
It will he seen that the testimony is British. 
Your essayist wrote to a number of British and 
American gentlemen connected with public insti- 
tutions, asking for information. The British 12 
CONSANGUINITY IN MARRIAGE. 
answered, but the Americans did not. The latter 
probably did not have the information, or were too 
busy looking after their political fences to impart 
it. Your essayist is under many obligations to the 
gentlemen from England, Scotland, and Ireland. 
CONCLUSIONS. 
1. Like breeds like, good or bad, entirely in- 
dependent of consanguinity. 
2. Evil results have undoubtedly followed 
consanguineous marriages, but whether dependent 
upon consanguinity is extremely doubtful. 
3. Intemperance, luxury, dissipation, sloth, 
and shiftlessness, as well as hygienic surroundings 
and innumerable other causes, among them the 
depraved moral state dependent on births the re- 
sult of incest, should bear much of the responsi- 
bility laid at the door of consanguinity. 
4. Testimony is often weakened by religious 
or other prejudices. 
5. Data are of doubtful reliability, full of 
flaws and false reasoning. The noted cases are 
the unfortunate ones. The favorable are unknown 
or forgotten. It is the ill news which travels fast 
and far. 
6. We as physicians know that there is much 
more illicit intercourse than is generally discov- 
ered. May not many people be related though not 
aware of it? Many marriages may thus occur 
between relatives presumed to be non-relatives, 
thus again vitiating statistics. 
7. Statistics show about the same proportion 
of deaf-mutes, idiots, and insane persons, descend- 
ant from consanguineous marriages, to the whole 
number of those unfortunates, as the number of 
consanguineous marriages is to the whole number E. 8. m’kEE, M. D. 
13 
of marriages. They show fertility among the 
consanguineous to be slightly greater than among 
non-consanguineous. They also show a somewhat 
greater frequency of retinitis pigmentosa. 
8. Atavism explains fully the fact that in 
some instances healthy consanguineous parents 
beget unhealthy children. This, as is well known, 
occurs in most hereditary troubles. Furthermore, 
a less superficial examination may show this 
healthful ness to he only apparent. 
9. Evil results in the offspring of consan- 
guineous marriages prove that something is wrong. 
That it was the consanguinity has not been proven. 
It may have been one of a hundred things, and 
dependent on all of the antecedents for genera- 
tions. Such results remaining absent after these 
marriages prove, for that case at least, that con- 
sanguinity was harmless, for it was known to he 
present. Further, if consanguinity was the cause, 
the effect should follow where the cause is present. 
10. Consanguineous marriages which bring 
together persons having a disease or morbid ten- 
dency in common are dangerous to the offspring. 
Not, however, one whit more so than the marriage 
of any other two persons not related, yet having 
an equal amount of tendency to disease in com- 
mon. Conditions present in both parents, good 
or had, are simply augmented, and the result 
would have been the same were they not related. 
11. Given, a malformation or disease firmly 
established, we have a tendency to breed true. 
Given, a defect or peculiarity in a family, race, or 
sect, this will naturally be propagated by inter- 
marriage, e. g., color-blindness is remarkably 
hereditary among the Jews and Quakers. The 
Quakers are educated to abhor color. Those who 
admire color separate themselves from the sect and 14 
CONSANGUINITY IN MARRIAGE. 
thus intensify the tendency in the remainder. The 
defect has probably crept among the Jews, and is 
kept up and intensified by intermarriage. The same 
means has also had its effect among the Quakers. 
12. Certain inherited diseases — as scrofula, 
phthisis, and rachitis — which are ascribed to con- 
sanguineous marriages, probably in every instance, 
could be traced back to an ancestor. 
13. Man is an animal, anatomically, physio- 
logically, and sexually. He is subject to the same 
laws of propagation. In-and-in breeding in 
animals is carried on to an extent not only not per- 
missible in the human species on moral grounds, 
but also beyond the bounds of human possibility. 
Yet this is done by cunning breeders to improve 
the stock and put money into their pockets. The 
Jersey cattle have been bred for the last hundred 
and fifty years on a small island, six by eleven 
miles. You would not raise them for beef or 
oxen, yet they command a high price for their 
milk and butter. This was probably the recom- 
mendation of the first cattle on the island, and 
this quality has improved from that time to this 
through in-and-in breeding. 
14. It would be better for the offspring were 
consanguineous marriages under medical super- 
vision. Certainly no better than for all marriages 
to be under like supervision. 
15. The half a hundred abnormalities ascribed 
to consanguinity, including almost all the ills that 
flesh is heir to — among others, whooping-cough — 
approaches the ludicrous. 
16. The factors which lead to consanguineous 
marriages are, portions of countries geograph- 
ically isolated or mountainous, rendering commu- 
nication with the outside world difficult; religious 
or political sects of an exclusive nature, and E. 8. M’KEE, M. D. 
15 
aristocratic ideas. As examples, note the percent- 
age of consanguineous marriages in Scotland, 5.25 
per cent., to those in England, 3 per cent.; the 
preponderance in Martha’s Vineyard, the com- 
mune of Batz, and among the Jews and Quakers. 
17. The facts do not warrant us in supposing 
that there is a specific degenerative effect caused 
ipso facto by consanguinity. 
18. Consanguineous marriages, no other ob- 
jection being present, should not be opposed on 
physiological grounds. 
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Falk: Zur Statistic der Taubstummen, Arch, fur 
Psycatrie, 1871. 16 
CONSANGUINITY IN MARRIAGE. 
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352 ; vol. iv., p. 332. 
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Monoyer, 5 ; Jeffries, 3 ; Simri, 3 ; Windsor, 1 ; Swanzy,. 1; 
Harlan, 1; Landolt, 1; Mooren, 8; Hocquard, 15. Total 
79; 18 were the descendants of cousins. 
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Hereditary Disease, with an appendix on Intermarriage, 
Inheritance, etc., London, 1843. 
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dans la commune de Batz, 1865; also, Memoires de la 
soeiete d’Anthropologie de Paris, vol. ii., 1865, p. 433. 
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N. Y. Med. Journal, June 13, 1885; also, Boston Med. and 
Surg. Journal, August 20 and 27, 1885; also, Wood’s Refer- 
ence Handbook of the Medical Sciences, vol. ii., p. 272. 
Walker: Intermarriage.