266 The Structure of Colored Blood- Corpuscles. 



each field of a drop, nor even in every drop of a person exam- 

 ined ; but I have not found any adult of either sex, from whose 

 blood the smaller extreme was absent, and only very few with- 

 out the larger. I have repeated the measurements of blood- 

 corpuscles without the addition of the reagent — both with and 

 without oiling the edges of the covering glass, i. e., with and 

 without preventing the ordinarily rapid evaporation — with prac- 

 tically the same results; drying of course contracts blood-corpus- 

 cles,and corresponding variations are observed. Some of the disks 

 are in outline not perfectly circular ; by measuring the largest 

 diameter of the largest, and the smallest diameter of the 

 smallest disks, the extremes I have met with in one and the same 

 specimen of human blood, are, as to the smallest, about the 



^-gVo-, an0 - as to tne l ar g es t, the -j-gVo of ai] inch (*• &•■> 0.00422 

 and 0.01016 Mm.). If the detached globules which I shall 

 describe, be counted as blood-corpuscles, there are even still 

 smaller ones. In each specimen of blood, the majority of red 

 corpuscles, however, are of about one size, which differs in dif- 

 ferent specimens, but is most frequently between the 38 1 7g and 

 the ^Vo °f an i ncn (-00655. — 00819 Mm.), or somewhere 

 about the -^^ of an inch (.0075 Mm.). The calculated aver- 

 age of the size of the red corpuscles in a drop, i, e., the arith- 

 metical mean of the measurements, is usually a little higher 

 than the size of the majority of the corpuscles. 



A very few, especially the smallest, but occurring excep- 

 tionally also among the larger, seem more or less globular ; 

 all others are bi-concave disks, the periphery being more shin- 

 ing and thick than the central portion. 



So-called "rosette" and " thorn apple " forms may be seen, 

 either immediately or in the course of a little while. I have 

 often watched the individual corpuscles while these forms, and 

 many others, were being produced; and in Part III of this 

 communication, I shall offer an explanation of their produc- 

 tion. 



Concentrating our attention upon the shape of the circular 

 disks, we soon find that the round outline of a few (and the 



