70 



ANIMAL PHYSIOLOGY. 



LESSON 23. 



FIG. 104. 



Blood corpuscles, Fowl. 



FIG. 105. 



blooded animals ; but the subjoined figure of the ostrich blood (Fig. 

 105), accurately copied from the preparation, 

 and carefully drawn to scale, tends to disprove 

 this assertion, as the corpuscles of the fowl, 

 both preparations being examined by a fourth 

 object glass, are certainly larger. 



If the ostrich has borne the reputation of 

 possessing the largest, there can be no doubt 

 that the beautiful little Musk Deer possesses 

 the smallest blood corpuscles of all the warm- 

 blooded animals. 



Magnified by a fourth object glass, they are 

 but infinitesimal specks (Fig. 106) ; for com- 

 parison, the blood of the mouse is shown (Fig. 107). 



393. In addition to the red corpuscle, all the vertebrate animals 

 possess also a colorless corpuscle (Fig. 108), which is uniformly 

 round, and possesses a variable number of granular bodies, or 

 nucleoli. 



These bodies may be seen (in the frog's foot) in the same vessels 

 with the red corpuscles; they are very sluggish, apparently possess- 



Blood corpuscles, Ostrich. 



FIG. 106. 



FIG. 107. 



FIG. 108. 



Blood corpuscles, Musk Deer. Blood corpuscles, Mouse. Colorless corpuscles, human. 



ing greater specific gravity than the red corpuscles ; they cling to 

 the sides of the vessels, and only move when struck against by the 

 red corpuscles. Occasionally it happens that a red corpuscle strikes 

 a colorless one up into the general current of the circulation, where 

 it circulates for a longer period than usual ; but as soon as the im- 

 petus of the blow begins to fail, it drops out (apparently by its own 

 weight), and once more clings to the sides of the vessel. 



394. The origin of the colorless corpuscle appears to be the fol- 

 lowing : the liquor sanguinis receives constant fresh accessions of 

 albumen and fibrine, the result of the digestion of the food. This 

 has a tendency to alter the specific gravity of that fluid (liq. san- 

 guinis) : if this were to take place, and the density of the fluid be- 

 come too great, the blood corpuscles (red) would scarcely be able to 

 move ; but if, on the other hand, it became too light, the red corpus- 



