312 Natural History Bulletin. 



puscles of minimum measure was only six, or less than one- 

 half of one per cent; and the total number which measured 

 the maximum was ten, or less than one per cent." 



As the result of a number of measurements made by 

 myself, I take as the average size of coloured corpuscles S/i, 

 or about S2\ns of an inch. 



JVtimber. — From a number of estimates made by the writer, 

 the average number of coloured corpuscles in each cubic mil- 

 limeter of blood from a healthy male somewhat exceeds five 

 millions. My enumerations were made with the Thoma h£em- 

 acytometer, made by Reichert, and with another of the same 

 kind made by Zeiss, as described by Limbeck. ^ 



Shape. — As they exist in the vessels, each coloured corpus- 

 cle is a biconcave disc, with smooth circular outline. After 

 being drawn for a few minutes, many become crenated. The 

 coloured corpuscles of some individuals become crenated 

 immediately on leaving the vessels, no matter how rapidly 

 the blood is brought between the cover and the slide. Usually 

 this change takes place only after several minutes. 



Roidcaiix. — When healthy human blood is placed between a 

 slide and cover glass properly, usually the coloured corpuscles 

 will tend to adhere to each other by their concave sides, form- 

 ing rolls very much like piles of coin. To these rolls the 

 term rouleaux is applied. Sometimes in blood that, aside from 

 this, appears to be normal, the coloured corpuscles do not 

 form rouleaux. 



Hcemogiobin. — Although not a microscopic character, for 

 clinical purposes an estimation of haemoglobin should accom- 

 pany every enumeration of coloured corpuscles. The instru- 

 ment used by the writer in these observations is the ordinary 

 Fleischl hccmoglobinometer, as described by Limbeck on page 

 17 of the work cited. This instrument is direct-reading, and 

 the standard of normal blood is 100 per cent. 



1 Grundriss einer Klinischen Pathologic des Blutes, von Limbeck. Gustav 

 Fischer, Jena. 1S92. p. 28. 



