354 COLLOIDS IN BIOLOGY AND MEDICINE 



Faradic current. Teased preparations of the nerves were then suit- 

 ably stained. The difference in the turgescence of the axis cylinder 

 was not only indicated by the different intensity of the stain, but also 

 by the fact that according to the salts employed, the axis cylinder 

 remained as thin threads or were swollen to broad bands, and that the 

 order in which the swelling was affected agreed with the lyo tropic 

 series characteristic of the loss of irritability. [W. BURRIDGE, loc. tit., 

 has adopted MACDONALD'S view that " in the excited nerve the pro- 

 tein aggregates are agglutinated to form aggregates of greater indi- 

 vidual size; this change is due to the reception of a negative electric 

 charge. As a result of this (K) salts are liberated which charge the 

 next segment of nerve negatively, and so excite it and leave the origi- 

 nal segment a positive charge. This positive charge determines the 

 return of the colloid of the original segment towards their former 

 state of aggregation." BURRIDGE considers that it is calcium plus 

 the negative charge which determines the coagulative change, and 

 sodium plus the positive charge which brings the colloids back to the 

 original state. Inhibition, according to this view, " is essentially a 

 decalcifying process." See also page 361. R. LILLIE, Science N. S., 

 Vcl. XI VIII, No. 1229, has offered an electromotor working model 

 of nerve conduction in the transmission of the active state along a 

 " passivated " iron wire. Tr.] 



Cerebrospinal Fluid. 



Our most sensitive instrument, the brain and spinal cord, is pro- 

 tected by a solid casing, the skull and spinal column. These latter 

 do not fit the nerve organ closely, but have a certain amount of dead 

 space which is filled with the cerebrospinal fluid. We may add that 

 both the bony case and the central marrow are covered with mem- 

 branes which are connected by a delicate mesh work. This network 

 is filled with fluid in which, to a certain extent, the brain and cord 

 float. It is a clear, colorless, aqueous fluid amounting to from 60 

 to 200 cc. in adults. Besides a very few formed elements it con- 

 tains 1/2 per cent of albumen. 



Several cc. may be withdrawn, by lumbar puncture, from patients, 

 without injury a procedure introduced by QUINCKE. This pro- 

 cedure has yielded valuable physiological and pathological data of 

 scientific and diagnostic importance. The fluid circulates constantly 

 and slowly. Under pathological conditions the fluid may be quickly 

 formed so that at times several liters may be lost through a fistula in 

 a day. 



There are two opposing theories of cerebrospinal fluid formation. 

 The one assuming a secretion has most supporters, whereas MESTRE- 

 ZAT, who asserts an " elective filtration," has fewer followers. MES- 



