84 THE AMERICAN MONTHLY [March 



Notes oQ Comparative Histoloi^y of Blood and Muscle. 



liv KDITH .1. CI^AYl")!,!-:, 



WKLKESI.EV, MASS. 



There is great difficulty iu basing «;eneral histology 

 oil the various books aud discussions of human histology. 

 Even if any mammal other than man is made the object 

 of study there is difficulty since many of t.he tissues of 

 the cat and rabbit for instance, vary widely from the 

 same tissues in man, while ainong the still lower forms 

 still greater diflerences exist. Compound tissues vary 

 largely and even many elementary ones are markedly 

 distinct. 



The animals chosen for these few notes were the rab- 

 bit, cat, pigeon, turtle, snake, frog, ambleptoma, crypto- 

 branchus, necturus; slightly aniia, a ganoid fish andpro- 

 topteus, adipnoan fish; only two tissues were examined 

 thoroughly, blood and stri[)ed muscle. Others are partly 

 worked out, but not fully enough for discussion. 



Blood. — This tissue has been very largely worked on 

 owing to its medico-legal importance, interest being cen- 

 tred in the size and number of the red corpuscles. These 

 cells of all animals fall into two natural groups, those 

 with, and those without nuclei. All mammals possess non- 

 nucleated corpuscles: vertebrates, birds, reptiles, amphib- 

 ians and fishes possess nucleated corpuscles. 



From various sources 1 have collected or made measure- 

 ments of as many forms in these classes as possible with 

 the following results placed in tabular form. 



These figures are suggestive. Variation occurs from 

 6 to 75 microns, a gradual decrease in size from general- 

 ized to specialized forms, both in different members in 

 the same class (salamanders, frogs, ca^cilians) and in the 

 dift'erent classes (amphibians, fishes, reptiles, birds, and 

 mammals). At each end of the table are specialized forms, 

 not equally so, but both far from primitive, modern 



