274 VESICULAR MATTER. 



dicate that Schwann's substance only discharges the physical duty of 

 an isolator. The coincidence between the varying activity of the nerv- 

 ous mechanism and the varying quantity of oxidized compounds of phos- 

 phorus in the urine indicates in a significant manner that this chemical 

 element bears something more than a passive relation to the processes 

 going* forward ; and its known occurrence in the vesicular structures, to- 

 gether with its extraordinary chemical relations, would prepare us to ex- 

 pect that it is, in reality, intimately concerned in all these phenomena. 

 Vesicular nervous material contains much less fatty matter than the 

 . tubular, but much more water. Thus HaufF and Walther 



Composition of 



vesicular mat- found in the gray substance of the brain from 85 to 86 per 

 ter ' cent, of water, and only from 4.8 to 4.9 of fat; but in the 



corpus callosum they found 70.2 per cent, of water, and from 14.5 to 

 15.5 of fat. From such facts it would appear that the presence of fat in 

 nervous material is functionally connected with its property of conduc- 

 tion or transmission of nervous influence. In the brain of a child which 

 died at birth, Schlossberger found that the corpus callosum contained as 

 much water as the gray matter, and that, compared with the brain of 

 adults, that of new-born infants is richer in water and poorer in fat. Von 

 Bibra ascertained that, within certain limits, the quantity of fat is con- 

 stant in the brain ; that a diminution or increase of fat in other parts of 

 the system is not accompanied by any change in the quantity of brain- 

 fat ; that the proportion of fat in the brain of man, other mammals, birds, 

 amphibia, and fishes, diminishes in the order in which their names are 

 here mentioned ; that the medulla oblongata contains the largest per- 

 centage of fat ; that the quantity of brain-fat in old men is a little less 

 than that of adults in the prime of life. He also concludes that the 

 amount of phosphorus in brain-fat is nearly the same in man, other mam- 

 mals, and birds ; that its percentage in the brain of the insane does not 

 exceed thef mean amount ; that the vesicular matter contains more phos- 

 phorus than the white; and that there is no special connection .between 

 the intelligence and the amount of phosphorus ; that the amount of fat in 

 the brain of the foetus is much less than that of the adult, the difference 

 being made up by an excess of water, but that a great and sudden aug- 

 mentation of fat occurs toward the end of foetal existence. 



Our attention may next be directed to the methods of repair of the 

 Mode of re air ves ^ cu ^ ar structures. Their waste, as just established, im- 

 of nervous plies their repair. Here, as in the muscular tissues, the 

 blood-vessels conduct both operations, and the mode of dis- 

 tribution of the capillaries is such as to bring the circulating current into 

 the most favorable position for discharging this duty. The vesicles are 

 included in the midst of a network of capillaries, and it is believed that 

 there, is a resemblance between their mode of growth and that of the cells 



