460 LESLIE B. AREY 



With the guinea-pig, rat, and rabbit I have obtained variable 

 results. The corpuscles of one guinea-pig examined in their 

 own serum were constantly discs; in another specimen, tested 

 twice in four days, it was impossible to find corpuscles except 

 in crenated condition; in a rabbit it was difficult to obtain prep- 

 arations which did not show extensive crenation in their own 

 serum; although human blood in this serum showed discs almost 

 exclusively. The blood of a white rat examined in its own serum 

 had one-half or more of the corpuscles strongly cupped; the 

 blood of two other rats examined in the serum of the first also 

 showed a majority of cups, although human blood corpuscles 

 remained discs. When serum from one of the last mentioned 

 rats was prepared its own corpuscles were discs, as were also 

 the corpuscles of the third individual. I have not worked on 

 many individuals of these species which have been used so ex- 

 tensively by other experimenters (Weidenreich, Lewis, et al.), 

 but the variable results just cited do not inspire confidence in 

 the employment of this class of animals; from my experience 

 they are untrustworthy and unfavorable material. The un- 

 tested suggestion presents itself that in those rodents which usu- 

 ally do not drink water, but depend on green vegetables for their 

 :supply, the concentration of the plasma may vary; external 

 temperature (the above tests were made in June) and the rations 

 lof the average animal house perhaps play no inconsiderable 

 role. 



2. Examination of circulating blood 



Blood observed circulating in the transparent parts of mammals 

 should furnish extremely reliable data concerning the question 

 at hand. There are, however, certain technical difficulties to 

 be overcome, as well as the infeasibility of observing rapidly 

 moving corpuscles under high magnifications. 



It is conceivable that the pressure on the deUcate vessels, 

 caused by the ordinary use of a cover glass and oil immersion 

 objective applied to the omentum (Jordan, Lewis, et al.) might 

 induce the assumption of the cup forms "through narrowing 

 the confines to which the delicate discs must adjust themselves" 



