476 ?HE BLOOD. 



together in rolls. These particles are red in colour, and vary 

 much in size. Their magnitude bears no proportion to the 

 size of the animal from which they are derived. Thus they 

 average about ^ooth of an i ncn i n diameter in the horse or ox, 

 but they are of a smaller size in the bat and mouse. In the 

 goat they are exceedingly small, measuring only -g-jV^th f an 

 inch. In the dog, as in man, they vary from Sfe * 00 th to 

 1J ^ ro .th. They are about one-third or one- fourth as thick as 

 they are wide. All these blood-discs are round in mammalia, 

 with the exception of the camel, dromedary, and llama, in 

 which they are ovoid. They are oval and nucleated in 

 reptiles. 



But floating in the liquid, in the field of the microscope, 

 may be seen, amongst the red particles just described, some 

 larger pale cells adhering to the glass in far less numbers 

 than the smaller red ones. They are in the proportion of 

 about one to thirty. 



The blood-particles are usually described as vesicular, the 

 red not having any nucleus, but the white possessing a single 

 or double nucleus, which is surrounded by granular matter. 

 Water is absorbed by, and alters the shape of, both white and 

 red particles. Acetic acid renders their envelope transparent, 

 and in excess destroys them. Both water and acetic acid tend 

 to show the nucleus of the pale corpuscles better than with- 

 out such an addition. The cellular nature of the blood-par- 

 ticles has been doubted by Robin, Dr Dalton of New York, 

 and Dr Lionel Beale. They think that the blood corpuscle 

 may be regarded as consisting of matter of different density 

 indifferent parts, being firm externally, but gradually becoming 

 softer, so as to approach to the consistence of fluid towards 

 the centre. 



The red blood-discs, if exposed to the air, shrink, become 

 angular, and acquire a variety of very singular shapes. These 



