Dear Doctor Sabin,
I shall be glad to examine some of the bone marrow from animals receiving the phospholipin intravenously. One would need as large a quantity as possible in order to obtain a workable amount of fat. It would probably be well--even necessary--to examine at the same time some normal bone marrow for comparison.
In the case of the omentum examined last year the procedure was as follows: You had the fresh material placed in alcohol-ether solution. The alcohol-ether soluble substances were obtained in the solution on filtering off the solid extracted omentum. A phosphatide or lecithin fraction was obtained after concentrating the above filtrate and precipitating with acetone.
Acetone-soluble fat was obtained by concentrating the filtrate from the phosphatide precipitation to dryness and extracting the residue with acetone. The acetone-soluble fat contained therefore all of the material, neutral fat or fatty acids, contained in the original omentum, that was soluble in acetone. All of the material obtained I returned to you--the amount was quite too small to serve for any chemical examination.
Your observations on the possible phagocytosis of the phospholipin and it disintegration before tubercles are formed is most interesting. For chemical analysis of artificial tubercular tissue, i.e. isolation of the peculiar fatty acid would require a rather large amount of material. It could be done but would be quite an undertaking, owing to the comparatively small amounts of the acid that could be present--since only small amounts of phospholipin are introduced into each animal.
I am awaiting with much interest your results with the antigenic serum and the possibility of building up protective antibodies by the direct introduction of the phospholipin--also your verdict regarding the liquid fatty acids from the acetone-soluble fat.
With the best greetings believe me
Most sincerely
Rudolph J. Anderson