230 



ANALYSES OF SYNOVIA. 



[BOOK i. 



death. Probably, in the most healthy condition, the serous sacs are, 

 as was said above, merely moistened with lymph, the excess finding 

 its way, as soon as it is formed, into the open mouths of the lymphatics. 

 Our knowledge of the physical characters and chemical composition 

 of the liquids of serous cavities is, therefore, almost entirely derived 

 from their examination when increased in quantity, and will be fully 

 referred to in the succeeding section of this chapter. 



The secretion of the synovial sacs of joints requires 

 a special description, as it differs in some important 

 particulars from the contents of the other serous sacs. 



Synovia is a transparent, faintly yellow, slimy liquid, of alkaline 

 reaction. It contains a larger proportion of solid matters than the 

 fluid of other serous sacs, and is specially distinguished from them 

 by containing mucin. 



According to the observations of Frerichs l whose analyses of 

 synovia are given below, the joints of animals which have been kept 

 at rest furnished more synovia than those in active exercise ; in the 

 latter it is more concentrated. 



ANALYSES OF SYNOVIA (FBERICHS). 



Cereforo- 

 spinal Liquid. 



Although not contained in a serous sac, the so-called 

 cerebro-spinal liquid must be placed by the side of the 

 liquids of serous cavities, inasmuch as it also is essentially identical 

 with lymph. It is a liquid which is contained in the meshes 

 of the sub-arachnoid connective tissue (as that tissue is called 

 which lies between the arachnoid and dura mater) and in the 

 ventricles of the brain, the latter being connected with the sub- 

 arachnoid space by a narrow canal leading into the fourth ventricle, 

 and sometimes termed the foramen of Magendie. A certain quantity 

 of cerebro-spinal liquid, which probably never exceeds two ounces, is 

 contained in the sub-arachnoid space during life, and permits of an 

 equalization of intra-cranial pressure under different conditions of 

 fullness of the cerebral blood-vessels. 



Cerebro-spinal liquid is alkaline, of low specific gravity (about 

 1005), and usually does not coagulate distinctly when heated, though 



1 Frerichs, quoted by Gorup-Besanez, Leltrbnch derpJnjs. Cliemie. 4te Auflage, 1873. 



