454 LESLIE B. AREY 



corpuscles are biconcave discs in Hogan's normal salt-gelatin 

 mixture which contains 2.5 per cent gelatin. 



But the foregoing evidence is not crucial. Blood is not a gel 

 at room temperature; neither does it contain gelatin; nor is 

 the arbitrarily chosen 3 per cent solution rational. If colloids 

 are to be added it is highly desirable to use the proper amount 

 of the protein normally present in blood. 



Beside fibrinogen these proteins are serum albumin and serum 

 globulin. Due to the conditions imposed by the world war I 

 was unable to obtain serum globulin but did procure a purified 

 sample of the closely similar serum albumin (Merck). To Ty- 

 rode's solution, which is claimed to duplicate accuratelj^ the 

 inorganic composition of blood, was added enough serum al- 

 bumin (re-dialized to make certain of its purity) to correspond 

 to the amount of both albumin and globulin normally present in 

 plasma. Blood corpuscles examined in this diluting medium 

 proved to be almost exclusively discs. 



Experimentation with undiluted blood is, at its best, unsatis- 

 factory. The crowded conditions, the tendency toward rouleaux 

 formation and coagulation which make such preparations un- 

 favorable are obviated by the use of diluting media. If, how- 

 ever, artificial 'physiological solutions' be used, the results may 

 ever, though perhaps unjustly, be subjected to criticism. At 

 best these are artificial media, the tonicity and colloidal consti- 

 tution of which may or may not simulate blood plasma. To 

 preclude such criticisms natural serum must be used. Accord- 

 ingly I had 20 cc. of blood drawn from my basilic vein. This 

 was defibrinated by whipping and centrifuged quickly; thus an 

 examining medium was obtained, identical with blood plasma 

 except for the loss of one of its minor protein constituents — fibrin. 



By utilizing an electrically heated warm-stage a hollow-cen- 

 tered life slide, cover glass, and the air of the cell itself may all 

 be maintained constantly at body temperature. A drop of 

 serum ^ was placed on a finger previously cleaned with alcohol, 

 and the finger pricked through the drop. The diluted droplet 



' Previous microscopic examination had made certain that the serum was free 

 from blood corpuscles. 



