THE EXPERIMENTAL PRODUCTION OF AN INTERNAL HYDROCEPHALUS. 437 



Protocol of Cat No. 99, adult male. 



December 17, 1917, 10:35 a. m. Under ether anesthesia, occipito-atlantoid punc- 

 ture, with release of about 1 c.c. clear cerebro-spinal fluid, was done. Slow subarach- 

 noid injection through this needle of 5.0 c.c. of a 5 per cent suspension of lampblack in 

 Ringer's solution. Normal and rapid recovery from ether; animal walked about room 

 within a few minutes. 



One hour later (11:45 a. m.) animal was returned to cage, active and playful. Ran 

 about as normal animal. 



Six hours later (5 p. m.) cat was in same active, excellent condition. Ran about cage 

 very rapidly. 



Ten hours later (9 p. m.) the animal was seen in a condition of cortical excitation. 

 The movements were usually rotatory in character, though always associated with con- 

 vulsive retraction of neck. Epileptiform jactitation of all four legs and of the body. Cat 

 can move about only in intervals of quiet between the attacks. 



The next day (Dec. 18) the cat was very lethargic and drowsy when undisturbed, but 

 it could be stimulated to run, when it staggered considerably. It was noted, "quite a 

 typical case of developing acute hydrocephalus." 



Animal remained lethargic, slow, and sleepy, but was able to move about quite well if 

 necessary. Quite inactive. On the sixth day the animal began to show a characteristic 

 weakness and droop in the movements of his hind-legs, with a strange and rather ataxic 

 lifting of the feet. Then after a few days (Dec. 29) the cat became "much more lethargic 

 and wobbly, * * * no longer able to walk or struggle along. Lies on side in cage all of 

 the time, weak and ataxic." 



The cat did not recover from this condition, but became progressively worse and died 

 on the sixteenth day (Jan. 2, 1918). It was injected with 10 per cent formalin through 

 aorta and the brain removed for study. A photograph of transverse sections of this brain 

 are given in figure 3. 



This protocol gives the reaction of the animal to a rather small dose of lamp- 

 black. Receiving only 5 c.c. of a 5 per cent suspension, it lived for 16 days, though 

 showing typical signs of an increase in intracranial pressure (lethargy, ataxia, etc.). 

 It has been found that if the concentration of the lampblack in suspension be 

 increased to 10 per cent the hydrocephalus is more acute and striking. Such 

 animals may go almost immediately through the stage of excitement, but show 

 the signs of pressure on recovery from the anesthesia. This phenomenon of an 

 acute increase in cerebral pressure seems the more likely to occur in older animals, 

 though absolute data on this phase can not be had, as the ages of the cats used can 

 be told only approximately. Obviously old cats (as judged by teeth, skin, activity, 

 etc.) have not, as far as this impression holds, shown the same .tendency to recovery 

 noted in the young adult animals. To a far greater degree, the age-difference in 

 reaction is brought out in the kittens, as already detailed. 



These adult cats, then, after subarachnoid injection of suspensions of lamp- 

 black, exhibit during life but little of interest in their reactions. In general, the older 

 animals show, within several hours, signs of disturbance of the intracranial pres- 

 sure; some pass through a stage of excitement, but most of them become immedi- 

 ately lethargic, weak, and ataxic. Some of these adult animals may recover, after 

 a couple of days, from the acute pressure changes and live for many weeks as fairly 

 normal animals. There is a striking difference in reaction after the inj ection, and due 



