LoESER, Functions of the Frogs Brain. 357 



the effects of the operation were present before one-half hour 

 after the operation, I called attention to this fact. 



Although I used a lens during the operation and post- 

 mortem, I made no microscopical preparations of the specimens; 

 therefore that degree of exactness which is obtainable by means 

 of microscopical preparations was not reached. 



By the term deficiency phenomena — as I use it in this 

 article — I mean those phenomena which are normally present; 

 but which are permanently — that is, for two and a half months 

 — absent after excision of a part of the central nervous system, 

 or permanently exhibited in a degree different from that in the 

 normal animal. 



Operations and Results. 



I. The first operation consisted in removing one cerebral hemisphere. As 

 a result, the animal displayed muscular weakness on the crossed side during 

 the first three days. Thus the frog, when jumping, turned slightly toward the 

 unimpaired side. Four days after the operation this temporary deficiency had 

 permanently disappeared. 



II. In the second operation I removed both cerebral hemispheres, and no- 

 ticed as a result bilateral muscular weakness lasting about three days and accom- 

 panied by subnormal skin reflexes. No deficiency phenomena were noticeable 

 the fourth day after the operation. 



III. The third operation consisted in burning out the thalamus opticus of 

 one side. The results were fewer voluntary movements ; bilateral defective sense 

 of touch, especially in the fore-limbs ; almost complete loss of sight on the crossed 

 side ; and weakness in the crossed legs. The first, second and fourth difficiencies 

 improved slightly during the first two weeks, but the sight defect remained un- 

 improved. 



IV. After burning both optic thalami with hot needles, sight was almost 

 completely abolished on both sides, and the animal was even more defective in 

 the sense of touch and voluntary movements than after operation III. All three 

 deficiencies showed practically no change during the two and a half months after 

 the operation. The marked parallelism between the loss of touch-sensibility and 

 voluntary movements was even more noticeable than after operation III. Flies 

 put into the cage after operations III and IV were never caught. 



V. The fifth operation consisted in unilateral burning out of the lobus and 

 thalamus opticus. The result was a complete and permanent loss of sight on the 

 crossed side ; forced movements straight ahead, which gradually improved ; 

 transient retention of urine, and reduction in voluntary movements and touch- 

 sensibility, exactly as noticed after removal of one thalamus opticus. Nearly all 

 of the animal's movements were at first forced — straight ahead — during which it 

 jumped higher and apparently with more vigor than normally. Stimulating the 

 frog caused it to jump so powerfully that it frequently injured itself. It assumed, 



