232 THE ANIMAL KINGDOM. 



by those which spread over them in the enveloping mem- 

 brane of the ear. 



They are the lowest order of animal cells, like the Algae 

 of the vegetable kingdom, without vessels of any kind, and 

 nourished by inhibition. 



THE TOE OF THE WHITE MOUSE. 



A very popular object, and worthily so. If the section is 

 thin, transparent, and perfect, it will show the structure 

 and position of the nail, the corium, and papillae beneath ; 

 the joints and shaft of each bone of the toe, with its attendant 

 arteries and returning veins ; also the hairs, with bulb and 

 follicle to each. In these hairs the outer cortical or invest- 

 ing membrane is distinctly seen, banded or crossed in the 

 centre with a double row of medullary cells. When these 

 last two slides have been looked at with a low power, 

 examine further with a half-inch. 



INJECTED PREPARATIONS. 

 THE KIDNEY. 



The Rabbit or the Cat gives an excellent preparation of 

 tin's organ. 



The whole substance of the kidney is made up of urinary 

 tubules, with attendant arteries and veins. These tubes or 

 passages are lined with cells like paving-stones, called 

 " epithelial cells," and those round bodies injected blue or 

 crimson are the Malpighian tufts, or terminations of a 

 tubule, into which an artery runs and twists about, forming 

 a plexus of minute blood-vessels, ultimately uniting to a 

 single outgoing or efferent vessel, which branches off again 

 into a capillary network, situated in the cortical or outer 

 substance of the kidney. These solitary efferent vessels are 

 like the portal-vein system of the liver, both serving to 

 convey blood between two capillary systems. The inter- 

 stices between the blood-vessels, nerves, and tubules of the 

 kidney are occupied by areolar tissue. 



