268 SOLID PARTS OF AMIMALS. 



bundle with the whole cord is covered by a continuation of the pia 

 mater. Very often different nervous bundles unite by false 

 anastomoses, the tubes of one bundle passing into another, and 

 running along with it ; yet two tubes never unite together so as 

 to become one, as happens with the blood-vessels. In the great 

 sympathetic minute-jointed or varicose tubes may be distinctly 

 seen mixed with larger cylinders. 



The first attempt to analyze the brain was made by M. Thou- 

 ret in 1790.* It was at that time that a vast number of dead 

 bodies which had been hurried in the Saintes Innocent burial- 

 ground in Paris were exhumed, and it was observed with some 

 surprise, that in many of these bodies the brain, after an interval 

 of a great many years, remained still unaltered, and free from 

 putrefaction. M. Thouret made some experiments on the brain, 

 in order to account for this long preservation, and concluded from 

 them that the brain is a soap, composed of an oily matter similar 

 (if not the very same) with spermaceti united to a fixed alkali. 



In 1793 M. Fourcroy published a set of experiments on the 

 brains of calves, sheep, and man. * He showed that the brain, 

 besides the animal matter of which it chiefly consists, contains a 

 small quantity of the phosphates of lime, ammonia, and soda ; 

 but no free fixed alkali, as Thouret had stated. He subjected 

 the animal matter of brain to the action of heat, of water, of sul- 

 phuric acid, of dilute nitric acid, of muriatic acid, and of alcohol. 

 The last reagent when boiled with brain dissolved a portion of 

 it, which was deposited, as the alcohol cooled, in brilliant plates 

 of a yellowish-white colour. This was the substance which 

 Thouret considered as analogous to spermaceti ; but which Four- 

 croy showed had no analogy whatever to that substance. He 

 considered it as constituting a peculiar substance differing from 

 every other ; (though he did not distinguish it by any peculiar 

 name,) but approaching nearer to albumen than to anything else. 

 In 1812, Vauquelin published a set of experiments on the cere- 

 bral matter of man and some other animals.! He treated the 

 brain successively with boiling alcohol as long as that liquid con- 

 tinued to dissolve anything; it deposited, on cooling, a white 

 matter in plates, the same as had been previously observed by 



* Jour, de Phys. xxxviii. 329. f Ann. de China, xvi. 282. 



\ Annals of Philosophy, i. 332, or Ann. de Chim. Ixxxi. 37. 



