182 



THE AMERICAN MONTHLY 



[October, 



blood-corpuscles. It maybe claimed 

 that the blood is that of a fowl. The 

 form of the corpuscles will distin- 

 guish them from those of mammalian 

 blood, but the corpuscles of cyclosto- 

 mous fishes are circular. 



In the second form of the question 

 it becomes necessary to discriminate, 

 if possible, between the blood of dif- 

 ferent mammals, especially to distin- 

 guish human blood from all other 

 kinds. Some say this is possible, 

 others that it is not. The discrimina- 

 tion depends upon the difference in 

 size of the corpuscles and our ability 

 to take cognizance of slight differences 

 of this kind. 



The speaker then discussed in an in- 

 teresting manner the subject of minute 

 measurements. The naked eye readily 

 divides a space of y^ of an inch into 

 four parts. The oval blood-disks of 

 Amphiumas measure -^^ X -3^-0 of 

 an inch, and the naked eye readily 

 notices the oval shape. But assuming 

 ^\-Q of an inch as the limit of meas- 

 urement with the naked eye, w^ith a 

 magnification of ten diameters the 

 eye could measure -^^-^ X 10 or yo\,-"o 

 of an inch with the same ease, or 

 TOO 00 with a_ power of 100 or yooVoo 

 with a magnification of 1,000. 



In measuring, the speaker prefers a 

 Jackson eye-piece micrometer, and 

 with this he finds yo^o~o ^^ ^'^ \nc\\ 

 equivalent to 30 spaces of the eye- 

 piece scale. Each space, therefore, 

 represents g-o oo" ^^ ^"^ inch, and since 

 a trained observer can readily divide 

 the single spaces of the eye-piece into 

 tenths, it is possible to measure the 

 ■sooVfo *^^ ^'^ inch, and by further 

 magnification this limit may be re- 

 duced to -5^0 oVoo <^f ^^^ inch. 



The difference in size of blood cor- 

 puscles is considerable ; in the ele- 

 phant they measure o^Q^-Q-inch, in the 

 musk-deer yg-g^oo* Blood-cells from 

 some different animals have the same 

 size. The corpuscles of human blood 

 and those of several animals have 

 practically the same dimensions. 

 Those of the opossum, for instance, 

 are about identical in size. Hence 



the microscope does not enable us to 

 distinguish human blood in every 

 case. The blood of the ox, which 

 measures ygJg-Q-inch, can be distin- 

 guished from human blood by the 

 difference in size. It has been ob- 

 served that the blood-cells may become 

 smaller than the normal size, but they 

 never increase beyond it. 



As regards the examination of 

 blood-stains, it has been found that 

 the corpuscles may be restored to their 

 normal size after years of dessicca- 

 tion by digestion in fluids. The ab- 

 normal corpuscles are not likely to be 

 restored. For this purpose the speaker 

 prefers pure water alone. Some years 

 ago a 33 per cent, solution of potash 

 was recommended. Water is now 

 used, and the results are surprising. 



The diameter of dog's blood-cor- 

 puscles has been observed to be uni- 

 formily g-g-^-g-o of an inch, although 

 prominent authorities have maintain- 

 ed that there was no difference be- 

 tween them and those of human 

 blood. 



At the conclusion of the address 

 the Secretary inquired if drying af- 

 fected the size of the cells, as had 

 been asserted by some writers. In 

 reply the speaker said he had never 

 found any appeciable difference be- 

 tween the cells measured in the serum 

 and v\^hen dried on a slide. The best 

 method of spreading the blood on a 

 slide for mounting was that of Prof. 

 Johnson. A drop of blood is placed 

 on a slide and spread by drawing 

 over it the edge of a second slide in- 

 clined. The smaller corpuscles to 

 be observed in this way are abnormal 

 ones, seldom found in the serum. 



In response to a question by Mr. 

 Hyatt, it was said that the size of red 

 corpuscles was not changed by dis- 

 eases. 



The range in size of human blood- 

 cells was stated to be -g-gVo ^'^ ToW 

 of an inch. 



On succeeding pages will be found 

 abstracts of the various papers read, 

 with the exception of three, of which 

 satisfactory abstracts cannot well be 



