THE PREPAEATION OF ANIMAL TISSUES. 49 



an inch long, and continue the hardening for an- 

 other week or two, as may be required. It may be 

 replaced by a 2 per cent, solution of bichromate of 

 ammonium for two weeks, and the pieces preserved 

 in spirit, or by Hamilton's method (chloral hydrate, 

 twelve grains, water, one ounce). The cere- 

 bellum, cerebrum, and, of course, the medulla 

 oblongata may likewise be hardened. In the case 

 of the two former, divide into suitable pieces to 

 ensure perfect penetration. 



The tendo achilles of the calf, and the metacarpal 

 nerve of the horse, each in inch-long pieces ; also 

 the posterior half of the eye-ball of a pig (for the 

 retina) may be hardened with advantage in this 

 fluid. 



Absolute Alcohol. 



This should have a specific gravity of 0*795. It 

 hardens in twenty-four hours, with much shrinking. 

 It is used for secretory glands, notably the pancreas, 

 which must be placed direct in it, or the gland may 

 spoil by partial self -digestion. The salivary glands, 

 the lachrymal glands, pieces from both ends of the 

 stomach for the gastric glands, the pancreas in 

 pieces, &c., should be placed in it at once. 



If the lymphatic gland of a horse, ox, or smaller 

 quadruped is injected with 2 per cent. Prussian blue 

 fluid by Klein's method (introduce a glass pipette 

 filled with the fluid into a lacteal near a mesenteric 

 gland and blow the solution into it), and then placed 

 in absolute alcohol, we have the lymph sinuses well 

 injected. The muscle structure of the beetle or 

 crab is shown well by placing a beetle or the ampu- 

 4 



