THE NERVES 355 



TREZAT'S " diffusion governed by osmosis " expressed in our terminol- 

 ogy is nothing other than ultrafiltration. 



GOLDM ANN'S experimental data, subsequently to be mentioned, 

 support this view, that the choroid plexus, the exceedingly vascular 

 membrane in the ventricles of the brain, serves as an ultrafilter. 

 [J. McCLENDON has recently offered additional experimental support 

 for this view. Tr.] 



Under pathological conditions the albumen content of the cerebro- 

 spinal fluid suffers very striking changes in which the globulin seems 

 particularly affected. On account of the minute amount of albumen 

 (0.5 per cent) the usual tests for albumen have been refined though 

 none have acquired the significance which has been won by "the 

 colloidal gold test" of LANGE. It rests on a modified clinical deter- 

 mination of the "gold number" (see p. 85), in other words upon 

 a measurement of the protective action on the gold hydrosol by 

 cerebrospinal fluid. Normal cerebrospinal fluid diluted with 4 per 

 cent saline has no effect in any dilution upon the red color of the 

 gold sol. If precipitation occurs at any dilution it indicates a path- 

 ological change. By this reaction, luetic affections of the central 

 nervous system are detected when the WASSERMANN reaction is still 

 negative and there are as yet no subjective changes. The reaction 

 also weighs in favor of diagnosing luetic disease (tabes, paresis, 

 cerebrospinal syphilis), when other diseases of the brain and cord are 

 in question. Meningitis, tumors, apoplexies are distinguished from 

 lues by a shifting of the precipitation zone. [Recently mastic solu- 

 tions have been employed for the same purpose. Tr.] 



Observations of KISCH and RUNERTZ indicate that under certain 

 pathological conditions (cirrhosis of the liver) the surface tension of 

 the cerebrospinal fluid varies from the normal. 



The Integument. 



Though other portions of the organism have greater or less capac- 

 ity to swell, this property is very much limited in the skin, epidermis, 

 hair, feathers, scales, etc. It is also evident that this limitation is 

 essential for maintaining shape and for retaining water within the 

 body. If the epidermis had unlimited swelling capacity like gelatin, 

 the fluids inside the organism would suffice to stretch the skin and to 

 enlarge it until all shape was lost, and finally the interior parts desic- 

 cated. Conversely, every natural atmospheric dampness and every 

 rainstorm still more would cause an almost unlimited addition of 

 water from the outside; a steady stream of water would flow through 

 the skin and the organs, and would be poured out through the kidneys. 

 Tf these opposing forces could still establish an equilibrium it would 

 vary so much in accordance with meteorological conditions that it is 

 hard to believe that the body would have any definite shape. 



