30 GLOBULES OF THE Br.OOD. 



Fig. 2. * 22. In man, the dog, the horse, and all other ani- 

 mals of the class of mammalia, the globules of the 

 blood are circular, (a. />.) 



23. In birds, reptiles, and fishes, the globules are 

 of an oval form, (c.) 



24. They are smallest in the mammalia, and largest 

 in reptiles and fishes. 



25. The blood of the mammalia and birds contains 

 the greatest number of globules. 



26. In animals with white blood, the globules are 

 colourless, generally circular, and very few in number. 



[ When these globules are carefully examined, with a powerful 

 microscope, it is seen that each one is composed of two distinct 

 parts, and that they consist of a sort of bladder or membranous 

 sack, in the middle of which there is found a spheroidal corpus- 

 cule, (a diminutive body.) 



[ Under ordinary circumstances, this bladder is flattened, and 

 forms, around a central nucleus, a circular border, of greater or 

 less depth, so that, as a whole, it presents the appearance of a 

 p. n disk, (a.) swelled or bulged in the middle. The 

 *$' ' external envelope of the globules consists of a 

 sort of jelly, which is of a more or less beautiful 

 red colour, and is easily divided: it is to the 

 presence of these vesicles, (little bladders,) that 

 the blood owes its colour. The central nucleus 

 of the globules is more consistant, and is not 

 coloured.] 



27. In its ordinary state, the blood is always fluid, and the 

 globules swim freely in the serum; but when drawn from the 

 vessels which contain it, and left to itself, it is not slow to con- 

 geal, and to present the phenomenon of coagulation. 



* Fig. 2. a, blood of a man, ft, blood of a sheep, c, blood of a sparrow. 

 These globules are magnified one thousand limes in diameter. 



t Fig. 3. , globule of the blood of a frosr, magnified about seven hun- 

 dred times, and seen in profile: 6, the same globule seen in front; the 

 envelope is torn so as to show the central nucleus. 



22. What is the form of the globules in the mammalia? 



23. In what class of animals are the globules oval? 



24. In what animals are they smallest? In what animals largest? 



25. What animals have the greatest proportion of globules in the blood ? 



26. What is the form and colour of the globules in white blooded animals? 



27. What is the ordinary state of the blood ? When drawn from the 

 vessels, and left to itself, what takes place ? 



