BODY TISSUES AND FLUIDS 471 



which has been called phrenosterol. Cholesterol is present chiefly in 

 the free state. 



Extractives. The most important nitrogenous extractives recognized 

 are hypoxanthin, and creatin, which is present to the extent of about 0.1 

 per cent. Among the amino acids isolated have been tyrosin and normal 

 leucin, or caprin. Lactic acid and inositol are also present About 1 per 

 cent of ash is present and thisi is composed in great part of alkaline 

 phosphates and chlorids. Potassium is probably the most important base. 



Cerebrospinal Fluid 



Normally the cerebrospinal fluid is a perfectly clear and colorless 

 fluid with a specific gravity of 1.005 to 1.008, and a solid content between 

 1 and 2 per cent The normal amount of spinal fluid has been estimated 

 roughly as 60 c.c., but pathologically the amount may be much larger, 

 especially in hydrocephalus. The trace of protein present in the fluid is 

 globulin in character. Fibrinogen and albumin are absent. The fluid is 

 hypertonic. It is probably formed by the secretory cells covering the 

 choroid plexus, according to recent studies of Gushing and his coworkers. 

 Its function is unknown. It would seem probable that the secretion of 

 the pituitary passes into the fluid. Normally not more than 3 to 5 white 

 cells per cu. mm. of fluid are present. 



From time to time many studies have been carried out on the spinal 

 fluid, although scarcely as accurate data are available as in the case of 

 blood, for the probable reason that the work has been carried out less 

 systematically. In the table below are given figures for the average normal 

 content of the various constituents in the spinal fluid, the data being taken 

 from various sources. From the figures given it is apparent that the 

 spinal fluid may be considered as a dialysate or ultrafiltrate of the blood 

 plasma. It contains very little protein so long as the fluid remains normal, 

 but nearly as much urea and glucose, and rather more salt than the blood. 



In pathological cases the properties may change, particularly in 

 meningitis. The fluid may be greatly increased in amount, under high 

 pressure, and have a considerable increase in protein. 



Denis and Ayer have presented recently some quantitative figures on 

 the protein content of spinal fluid. Normally they found the fluid to 

 contain from 0.04 to 0.1 per cent of protein. In active tabes, moderately 

 active syphilis of the nervous system and lethargic encephalitis the protein 

 content ranged from 0.1 to 0.2 per cent, in recent cerebral vascular 

 disturbances such as hemiplegias and cerebral embolus from 0.1 to 0.3 per 

 cent, in acute syphilis of the nervous system and general paresis from 0.2 

 to 0.6 per cent, while in tubercular and acute meningitis such high figures 

 as 0.2 to 1.0 and 0.4 to 1.3 per cent respectively were observed. By taking 



