356 Journal of Comparative Neurology and Psychology. 



during the operation. The skin ov^er the cranium of the frog 

 was first washed with a weak solution of bichloride of mercury, 

 which was immediately removed with sterilized cotton and then 

 Avith 95 ^ alcohol. The instruments and the hands of the oper- 

 had been previously sterilized with 5 ^r carbolic acid, followed 

 by 95 % alcohol. 



An incision was made through the skin of the cranium, fol- 

 lowing the mid-dorsal line. The skin was held apart by a pair 

 of weighted hooks, and an opening was made with a small tre- 

 phine through the cranium over the part of the brain to be re- 

 moved. Since the two occipital arteries take their course later- 

 ally, this opening was made as near as possible on the mid-dor- 

 sal line of the cranium. With a delicate pair of forceps small 

 pieces of the cranial bones were carefully broken away to make 

 the primary opening of sufficient size for the operation. Great 

 care was taken not to injure the meninges and the vessels of the 

 choroid plexus therein. A i ^, solution of adrenelin was used 

 with great success whenever injury to the choroid plexus, or 

 even the internal carotid and branches caused profuse hem- 

 orrhage. 



A small pointed knife and a very fine needle were used for 

 excising or burning the different parts. Ringer's solution was 

 used to moisten the wound after the operation. No antiseptics 

 were used in the wound, which was closed with sterilized silk 

 sutures. The animals were kept isolated in moist moss, which 

 was frequently changed. At first they were observed two or 

 three times a day, but, after several days, once a day, and after 

 seven to ten days, once every two days was sufficient. Most of 

 the frogs were fed after the operation; a few — depending upon 

 the nature of the operation — were soon able to catch flies. The 

 observations were tabulated, dated, and later the post mortem 

 findings were added. Two animals were used for each opera- 

 tion, and the reactions compared with one another and with the 

 reactions of normal frogs. 



I seldom noted the immediate effects within one-half hour 

 after the operation, since they were obscured by the effects of 

 the ether. In some instances where it was quite evident that 



