176 ON VARIABILITY AND ADAPTATION 



the calcium globules would seem to be relatively solid, the others 

 relatively liquid. But by no means was I able to gain the 

 phenomenon with simple soaps of palmitic and stearic acids : 

 on cooling concentrated solutions they passed immediately into 

 the true crystalline form, and as these palmitic and stearic soaps 

 are solid and definitely crystalline at the room temperature, it 

 seemed evident that the spherules seen in the organism at room 

 temperature could not be of palmitin or stearin compounds, or 

 at least could not be simple uncomplicated compounds of the 

 same. It is possible, I would suggest, that compounds con- 

 taining palmitic or stearic, along with oleic, acid may be fluid 

 at room temperature. 



Here I trust that you will not misunderstand me. I do not 

 in the least wish to suggest that the doubly refractive bodies 

 seen in, or gained from, the tissues are simple soaps of oleic acid. 

 The very instability of the oleates of ammonia, sodium, and 

 potassium renders this most unlikely. All I wish to show at 

 this stage is that we have a group of relatively simple bodies 

 of known composition, of bodies having these curious physical 

 properties that are likewise possessed by the myelin of the 

 organism, and to suggest that a study of these simple cases is 

 calculated to throw light on the more complicated. This 

 certainly it has accomplished, and here, before referring to our 

 studies on more elaborate compounds, it is fitting and timely 

 that I should indicate how the study of the simple soaps afforded 

 us what I believe to be a most important clue to the nature and 

 properties of the myelins in general. 



I have already mentioned that, studying strong solutions of 

 the simpler soaps, these remarkable doubly refractive globules 

 make their appearance as the solution undergoes cooling. Time 

 and again the appearance is transient. At one moment the 

 whole field of the microscope may flash out into a rich clustered 

 constellation of bright crosses to be followed almost immediately 

 by complete crystallization of the whole area. This fact alone, 

 not to mention the doubly refractive nature of the globules, 

 indicates that they are akin to crystals. Obviously they are 

 not crystals proper ; the form is not that which we associate 

 with crystals ; they are globular, not angular ; they have all 

 the appearances of being fluid bodies and not solid ; in water 

 they do not dissolve as do ordinary crystals, but swell up and 



