174 ON VARIABILITY AND ADAPTATION 



words, that calcium soaps become formed. From these observa- 

 tions he was led to study, histologically and chemically, areas of 

 pathological calcification in the organism in order to determine 

 if these afforded indications that the fats play a part in the 

 process of pathologic calcification, and more particularly if there 

 were indications of the presence of soaps as an intermediate 

 stage in the process. He found that outside the body the stain 

 Sudan iii affords a differential staining between neutral fats and 

 soaps, globules of the latter taking on a paler, more yellowish 

 tinge, and that in the zone immediately surrounding areas of 

 active calcareous deposit he could recognize similarly globules 

 taking on the deeper stain of neutral fats, together with others 

 taking on the characteristic tint of soaps. 



From these studies Klotz concluded that fats play an active 

 part in the process of calcification : that, first, the affected 

 area undergoes necrobiosis with fatty degeneration ; that, next, 

 calcareous soaps become formed, and, finally, that the fatty 

 acid moiety of the compounds becomes replaced by the chemi- 

 cally more powerful phosphoric or carbonic acid, calcium phos- 

 phate and calcium carbonate being the end products. The 

 indications were that he had not to deal with a simple calcium 

 soap, but with a soapy compound containing calcium and, as 

 he held, a proteid constituent. These stages could be well 

 followed in that commonest seat of calcareous degeneration, 

 namely, the aortic wall in the course of arterio-sclerosis. But 

 now, happening to visit Marburg for other purposes, there 

 Professor AschofE pointed out to me that Dr. Klotz's description 

 of these fatty globules, which were not fat but of a soapy nature, 

 seen in the atheromatous area, corresponded in many respects 

 with that of the globules seen by him in the arterio-sclerotic ' 

 artery, globules which, as Mettenheimer first showed, and as 

 Torhorst, working in AsehofE's laboratory, had independently 

 determined, are doubly refractive. They are, in short, myelin 

 bodies. 



Were Klotz's Soaps and these Myelin Bodies 

 one and the same ? 



It was to the solution of this question that AschofE and I 

 directed our attention. We found, in the first place, that the 



