i82 Journal of Comparative Neurology. 



tivity of our thoughts. There is an irritabiUty of the nervous 

 tissue which is the product of exhaustion and an evidence of 

 its defective nutrition, or what is equivalent, of its overstimula- 

 tion. This irritability simply means weakened mhibition, which 

 is as surely a sign of exhaustion as is the want of the power to react 

 to an impression. Repetition of this prolonged hyperaemia leads 

 to its easier production. The nutrition of the cells soon becomes 

 permanently modified. They energize dift'erently. The vessel 

 walls become permanently distended. They are not equally 

 strong at all points and aneurismal dilations or pouches form 

 along their course. Obstruction results to the blood current. 

 Nutrition is more greatly impaired. The contents of the vessels 

 transude through their walls under the increased pressure and 

 block up the peri-vascular lymph spaces. The changes in the 

 vessel walls also favor this. The flow of the waste products is 

 obstructed and the cells become bathed in the products of 

 their own metabolism. The toxic effect of these still fur- 

 ther deranges their functional activity. Permanent degen- 

 eration of the cells soon ensues. They change in form, 

 their prolongations become rounded off, their interior becomes 

 granular, or is filled with fat globules. The delicate plexus 

 from which springs the afferent nerve fibrils is permanently 

 damaged. The scavenger cells become enlarged, more visible 

 and filled with the products of cell degeneration. Finally the 

 entire cell is removed or so disorganized that its distinctive fea- 

 tures entirely disappears. These changes are seen in exag- 

 gerated degree in such forms of mental disorders as paretic 

 dementia, in which the nutritive changes and consequent loss of 

 power are rapid and marked. 



Bear in mind that in all these cases the incipient change, 

 the first step in the degenerative process, is a simple error in cell 

 nutritive, an interference with the opportunity to secure sufficient 

 nourishment and a demand for more energy than the supply 

 given will produce. When the problem is in its simplest form 

 its solution should be comparatively easy, let it become complex 

 through the lapse of time and its solution is no longer possible, 

 when the vessel walls become changed in character or even 

 dilated permanently, the recuperation is slow and does not 

 always advance with the improvement in the general condition 



