180 PHOSPHORUS SEEMS ESSENTIAL 



acid is in many of its characters very similar to the 

 fatty acids, but is essentially distinguished from them by 

 containing nitrogen. The organic constituents of bile 

 resemble the acid resins in physical characters, and yet 

 contain nitrogen. The organic alkalies are intermediate 

 in their physical characters between the fats and resins, 

 and they all contain nitrogen. A nitrogenized fatty acid 

 is as little improbable as the existence of a nitrogenized 

 resin with the characters of a base. 



96. An accurate investigation would probably dis- 

 cover differences in the composition of the brain, spinal 

 marrow, and nerves. According to the observations 

 of Valentin, the quality of the cerebral and nervous 

 substance is very rapidly altered from the period of 

 death, and very uncommon precautions would be re- 

 quired for the separation of foreign matters, not prop- 

 erly belonging to the substance of the spinal marrow or 

 brain. But, however difficult it may appear, the inves- 

 tigation seems yet to be practicable. We know, in the 

 mean time, that all experience is against the notion of 

 a large amount of carbon and hydrogen in the substance 

 of the brain. The absence of nitrogen as an element 

 of the cerebral and nervous matter, appears, at all 

 events, improbable. This substance, moreover, can- 

 not be classed with ordinary fats, because we find the 

 cerebric acid combined with soda, whereas, all fats are 

 compounds of fatty acids with oxide of glycerule. In 

 regard to the phosphorus of the brain, we can only 

 guess as to the form in which the phosphorus exists. 

 Walchner observed recently, that bubbles of spontane- 



