PHYSIOLOGICAL CONCLUSIONS. 119 



Chemistry is too intimately associated with all the most important 

 questions concerning the theory of the nerves to be excluded from 

 its just participation in the study of that most noble of all animal 

 matters in which are concentrated the highest vital functions. 

 The share taken by chemistry in the explanation of the functions 

 of the nervous system is now so thoroughly and fully admitted 

 that it is unnecessary to enlarge upon this point. In corres- 

 pondence with the physical and physiological phenomena of the 

 nerves, we find a substance accumulated in them which exhibits 

 such mobility in reference to its proximate constituents as is 

 not to be met with in any other organ of the animal body ; the 

 chemical phenomena very probably, therefore, stand also here in 

 the closest relation to the physical and physiological. Scarcely 

 any one can entertain the idea that the nerves which (as Ludwig* 

 has shown in his admirable Memoir on the influence of the nerves 

 upon the salivary secretion) co-operate directly in the elaboration 

 of certain secretions from the blood, and influence their accelerated 

 or modified separation, can control such functions without under- 

 going chemical change. The chemical substrata of the nerves are 

 conformable to their functions ; for, as in all other organs, the 

 physiological importance of the chemical constitution, and the 

 relations of affinity between the chemical substrata, must accord 

 with one another. (See vol. i, p. 25.) 



The analysis of the nervous tissue is obviously still very imper- 

 fect, as must be seen from the above remarks. 



The most suitable object for an investigation of this kind is 

 probably the white matter of the hemispheres of the cerebrum, if 

 we have reference only to the facility with which considerable 

 quantities of it may be obtained. The white matter is far pre- 

 ferable to the grey, as it contains fewer blood-vessels, no nerve- 

 cells, and scarcely anything but nerve-fibres. 



In making the determination of the quantity of water, the same 

 precautions are required as in the case of every other organ, and 

 especially of the muscles. We have already shown the importance 

 of such precautions in our observations on the latter organs. 



In determining the mineral constituents of the cerebral matter, 

 it must be borne in mind that the ash exhibits an acid reaction 

 from the presence of free phosphoric acid, and that it, on that 

 account, generally encloses a considerable amount of carbon. As 

 is well known, phosphorus is given off in a volatile form when 

 carbon is heated with phosphoric acid or with acid phosphates, 

 * Mitth. d. Zurch. naturf. Gesellschaft. No. 50, 1851. 



