436 THE EXPERIMENTAL PRODUCTION OF AN INTERNAL HYDROCEPHALUS. 



From such findings and changes in the head, as given in the foregoing para- 

 graphs, the diagnosis of an internal hydrocephalus in these kittens has been very 

 easy during life. The kittens show practically every sign noted in the more chronic 

 cases in children. Palpation of the head gives unmistakable evidence of fluctua- 

 tion of a fluid; pathologically the diagnosis is confirmed. Examinations of the 

 fundus of these kittens' eyes have been attempted but have not proved satis- 

 factory. The control animals of the same litter (subjected to no experimental pro- 

 cedure) have shown no variation from the normal, nor have those other control 

 animals, subjected to similar injections of other insoluble granules (usually cinna- 

 bar, fig. 8). Thus each experimental kitten was controlled by an unoperated animal 

 and by another in which analogous granules were injected. The relation of the 

 injection of lampblack to the later occurrence of hydrocephalus seems established. 



ADULT CATS. 



All of the adult cats used in this series were given subarachnoid injections of 

 lampblack through lumbar or occipito-atlantoid needle. No ventricular injections 

 were made, as interest was chiefly lodged in the production of hydrocephalus from 

 intrameningeal injection. In all, 18 adult cats were subjected to such subarachnoid 

 injections; of these, 12 received lampblack; 4 cinnabar; 1 lycopodium; and 1 "car- 

 bon flour." Of the 12 receiving the regular lampblack, 4 died within the first 5 days 

 after the experimental procedure. The longest period of survival after the injection 

 was 22 days. On the other hand, the cat injected with "carbon flour" lived 4 months 

 before being sacrificed, while the cat given lycopodium into the subarachnoid space 

 was not killed until after 5 months. The cinnabar animals varied in length of life 

 after injection from 3 days to 2 months; most of these were sacrificed at the time 

 when the lampblack animal in the same series died. Thus, the shorter period of 

 survival in cats receiving lampblack as compared to others in the series is striking. 



The difference in reaction of the cats to such subarachnoid injections, as com- 

 pared to the kittens, can be made out by observation of the animals soon after 

 injection. For the most part, signs of increased intracranial pressure were present 

 the next morning after the injection; the animals would be lethargic, sleepy, and 

 could not be roused. In the more profound cases the animals were found lying on 

 their sides and finally went into coma. The onset of these signs of intracranial 

 pressure frequently occurred within 12 hours; in all of the severe cases the phe- 

 nomena were obvious within 24 hours. In such experiments, from the experience 

 with kittens, it must be assumed that there is no possible enlargement of the 

 cranial vault or other compensation for the acute increase in intracerebral pressure. 

 The results, in consequence, are not as interesting or as striking as in the kitten, 

 where compensation is possible. 



Some of these adult cats with such an experimental, acute obstruction to the 

 flow of cerebro-spinal fluid went through a stage of marked cerebral excitation. 

 The protocol of one such is given below, as it illustrates graphically the onset of the 

 acute pressure-increase and the later conversion into the stage of lethargy and 

 helplessness. 



