1899.] on Structure of the Brain in Relation to its Functions. 133 



repose and activity of the brain. I am inclined to believe that 

 Lugaro's view is the better one : that cerebral activity is associated 

 with a cutting off of the great majority of interneuronic connections, 

 and the strengthening of the current traversing a few ; that during 

 repose or under narcotics there is a general expansion of the gem- 

 mules due to exhaustion of their contractility, and thus all the 

 neurones being in contact, nervous currents are so. diffused that they 

 are not of sufficient intensity to rise into consciousness. 



A new method of staining has revealed a fact concerning the 

 internal constitution of the neurone. There are two biochemical 

 substances entering into the formation of the neurone — a substance 

 stainable by aniline dyes which exists in the body of the cell and upon 

 the protoplasmic processes, and another unstainable substance which 

 forms the framework of the cell, and consists of extremely delicate 

 threads which pass into and form the processes. This latter is the 

 essential conducting agent, and upon its integrity the life of a neurone 

 depends. The stainable substance is probably a store of food or 

 energy which is continually used up during functional activity, and 

 replaced and stored up during rest from the surrounding lymph (Figs. 

 10 and 11). 



The arrangement of this colouring matter in the cell serves as a 

 means of distinguishing cells with different functions ; for example, 

 the large motor cells of the brain, with a characteristic arrangement 

 of the stainable substance, are found only in the central regions of 

 the cortex, and in the occipital lobe ; they do not exist in the associa- 

 tion centres. This is possibly a proof of relation of structure of the 

 neurone to its function. 



Very little is known of the chemical composition of the nervous 

 elements, only that they are among the most complex bodies on our 

 planet. When they die they split up into simple bodies, and this 

 fact has served a most useful purpose in following the course taken 

 by nerve fibres ; e. g. if a motor nerve of the brain is separated from 

 its cell by injury or disease, the fibre below the injury undergoes 

 degeneration which can be recognised by the chemical changes 

 occurring in the fibre during its destruction. We can follow this 

 dead fibre to its ultimate destination by the microchemical reactions 

 of the products of degeneration even though they extend for more 

 than a yard in length. Besides this there is a change in the life of 

 the cell body itself when the fibre is cut ; for the stainable substance 

 disappears, and only reappears if a new fibre grows out from the 

 cell. 



In this address I have attempted to give you a sketch of what we 

 know and what we believe we know of the relation of the structure 

 of the brain to its functions. The vast problems of mind still remain 

 unsolved ; but the conception of the neurone as an independent unit, a 

 microcosm within a macrocosm, has shed a flood of light upon the 

 problems of disease of the nervous system, and if further evidence is 



