The experiments which have been presented show that the spinal fluid occupies a unique position among the fluids which accumulate in serous cavities of the body. It contains normally neither proteolytic enzyme nor anti-enzyme, whereas blood serum, from which it is derived, exhibits both enzymotic and anti-enzymotic activity.
In the blood anti-enzyme greatly predominates over enzyme, so that proteolysis does not occur, unless the anti-enzymotic power of the serum has been destroyed by the addition of acid. In pathological conditions both enzyme and anti-enzyme may make their appearance in the spinal fluid. With inflammations of other serous cavities of the body the anti-enzyme of the exuded serum as a rule preponderates over and restrains the activity of the proteolytic enzyme freed from leucocytes. On the other hand, in infection of the meninges with Diplococcus lanceolatus and with Streptococcus mucosus free proteolytic enzyme has been present in considerable amount in four of five fluids which have been tested. Free proteolytic enzyme has not been observed in the spinal fluid in cases of epidemic meningitis.
The cases which have been studied demonstrate that in epidemic meningitis some anti-enzymotic action may be present in the early stages of the disease; but it tends to disappear rapidly so that anti-enzyme seems to be constantly at a low ebb. It is possible that the absence of anti-enzyme in normal spinal fluid, and the tendency for it to disappear so much more rapidly than in other inflammatory exudates, may explain in part the severity of acute meningeal infections.
Non-inflammatory transudates into the subdural spaces differ from inflammatory exudates in that the inhibitory element of the blood serum accumulates, and this accumulation suggests an interference with the elimination of the antibody from the spinal fluid. Such interference is not evident in so-called serous meningitis.
In content of anti-enzyme the spinal fluid of chronic conditions, such as tuberculous meningitis, apparently occupies an intermediate position between acute inflammation and serous effusion, and five of seven tuberculous fluids which were tested exhibited various degrees of anti-enzymotic action.
Variations in content of enzyme and anti-enzyme, noted above, may depend upon the rapidity with which the fluid, carrying the elements mentioned, enters the spinal cavity, as well as upon the rate of their elimination from the spinal fluid. Subdural injection of large quantities of anti-meningitis serum (horse's blood serum) does not increase the anti-enzymotic activity of fluids withdrawn twenty-four hours after its injection; disappearance of anti-enzyme being caused by rapid elimination of serum from the spinal fluid.