410 



swelling ought also now to take place and produce irregular bell- 

 shaped forms. Moreover, both Weidenreich and Lewis regard a 

 17o osmic acid solution as a good fixative for blood corpuscles and 

 one in which they retain their normal form: cup-shape. But in fixing 

 one is dealing primarily with a process of coagulation. While the 

 erythrocytes are still separate the unequal contraction of coagulation 

 will produce irregular shapes including "cups" and "saucers"; when 

 the corpuscles have become arranged in rouleaux they have also be- 

 come fortified against distortion and so persist as contracted but still 

 biconcave discs. 



Weidenreich seeks to show further that the shape of the erythro- 

 cytes, besides being dependent upon the osmotic pressure of the 

 medium, depends also upon its colloidal composition. Thus erythro- 

 cytes are bell-shaped in "a 0.9% plasma" solution. In a 0.9 7o NaCl 

 solution they are biconcave discs. However, when gelatin is added 

 to the latter, the cells again become bell-shaped. The argument seems 

 to have little force since we do not yet know the full complement of 

 physico-chemical changes that transpire in a solution of NaCl to which 

 gelatin is added. It is probable that the gelatin molecules absorb 

 Na and CI ions and so leave the solution hypotonic and compel the 

 corpuscles to assume shapes typical for such solutions. Nor does it 

 appear that "a 0.9 7o plasma" solution is isotonic with blood serum, 

 even though the corpuscles do maintain the bell shape (the assumed 

 normal form) in this colloidal substance. Indeed since solutions of 

 colloids are known io have scarcely a measurable osmotic pressure, 

 the solution is in reality hypotonic, and contains the cells in shapes 

 expected. The 0.9 '^/q NaCl solution, which is very close to isotonic, 

 on the other hand, would be expected to contain the normal forms, 

 or biconcave discs. 



Lewis states that in blood from the finger placed on a warm 

 slide, cup-shaped corpuscles are seen in active motion. The latter are 

 said to assume the form of biconcave discs as the slide cools and the 

 corpuscles come to rest. The writer has been unable to trace an in- 

 dividual cup-shaped corpuscle under these conditions, into a disc- 

 shaped form, nor is this much claimed by anyone else as far as he 

 knows. It is true that as the slide cools rouleaux are formed, and 

 the number of discs seems to be increased for more are seen on 

 edge. The very motion of the corpuscle on a warm slide may cause 

 it to become cup-shaped. Under the conditions to which the deli- 

 cate red corpuscles are subjected for examination one could only 

 expect them to assume various shapes (as they actually do) among 



