SOAPS AND MYELINS 175 



globules in the atheromatous aorta, which under Nicol's prisms 

 were doubly refractive, take on the differential stain with 

 Sudan iii ; that Torhorst's myelin and Klotz's soaps are iden- 

 tical. The methods for isolating fats and soaps are still so im- 

 perfect, and the amount of the doubly refractive material in the 

 atheromatous aorta relatively so small, that chemical isolation 

 and study appeared hopeless. All that was left was to study 

 the physical properties of various soaps and lipoid bodies so 

 as to determine which of them approached most nearly in 

 properties to the myelins. Thus it was that I undertook a 

 long series of observations, in association with Professor Aschoff, 

 beginning with the various simple soaps, to observe whether 

 they possessed the power of forming these characteristic doubly 

 refractive globules. 



That certain soaps under certain conditions produce myelin 

 bodies has been known for long x and has been the subject of 

 study, more especially by Quincke. One has but to take a drop 

 of oleic acid on a slide and surround it with strong ammonia 2 

 to obtain immediately a brilliant development of myelin figures, 

 and, what is more, these figures examined between crossed 

 Nicol's prisms are doubly refractive (Plate III. Fig. 1). We can 

 produce " myelin forms " from an ammonia soap. This, however, 

 is not quite the same thing as reproducing the characteristic 

 doubly refractive spherules such as we have seen in the tissues of 

 the organism. Briefly, I may state here that with certain simple 

 soaps it is possible to gain these spherules, and that by very 

 simple means, namely, by taking the pure soap with a small 

 quantity of water on a slide, warming it until it dissolves, and 

 then as it cools it may be that under the polarizing microscope 

 a perfect rain of spherules shows itself. In some cases these 

 persist for hours and, indeed, for days ; in others, depending 

 on the nature of the soap, they are transient, appearing for a 

 moment and immediately giving place to a brilliant white layer 

 of formed crystalline plates. 



By this means we determined that simple soaps of oleic acid 

 give these figures — oleate of ammonia, of sodium and potassium, 

 so also those of calcium — but here appeared to be a difference : 



1 Neubauer in the 'sixties seems to have been the first to make the 

 observation. 



2 The experiment is more striking, as noted by Lehmann, if the ammonia 

 and oil be coloured by contrasting dyes. 



