308 PROFESSOR C. R. MARSHALL ON 



In frogs pithed anteriorly to the optic lobes, convulsions similar to those occurring 

 in a normal frog were produced by tutin, but after destruction of these lobes muscular 

 stiffness only resulted. 



In rabbits and cats which had the brain above the pons removed convulsions were 

 still produced by tutin (figs. 4-6) ; and when the brain was divided just behind 

 the pons, muscular stiffness and increased reflex excitability were produced by its 

 administration, but less readily than convulsions with the pons intact. With the 

 quadrate bodies in place, convulsive movements seemed to be somewhat more easily 

 induced than when the section was made immediately in front of the pons. One 

 cannot, however, be dogmatic on this point. In an experiment (rabbit, 1575 grm.) in 

 which the brain was cut through in front of the corpora quadrigemina, and the 

 anaesthetic subsequently stopped, the convulsions induced by 10 mg. tutin intraperi- 

 toneally were diminished but not abolished by section between the anterior and 

 posterior bodies (the hind limbs still twitched), but all limb movements ceased after 

 section behind the posterior bodies. There can be little doubt that shock played an 

 important part in producing this result ; but nevertheless it gives some support to the 

 view expressed that the presence of the mid-brain increases to some extent the 

 susceptibility to tutin. 



Notwithstanding the susceptibility of the lower centres of the brain to this substance, 

 the cortical centres are probably mainly affected under ordinary circumstances. This 

 is suggested by the following experiment. A cat (1750 grm.) was anaesthetised with 

 chloroform and the anaesthesia maintained with ether, and at 3.30 the left cerebral 

 hemisphere was removed. The fore limbs were connected by cords working over 

 pulleys to weighted levers which registered their movements. A.t 4.0, 0"001 grm. tutin, 

 and at 4. 1 6, 0'0005 grm. tutin, were injected intravenously. Slight movements of the left 

 fore foot occurred at 4.19; and at 4.20 short tonic contractions with superposed 

 clonus developed. These continued at irregular brief intervals for seventy seconds, 

 when a well-marked and prolonged tonic-clonic convulsion occurred, which gave place 

 to the convulsions shown in fig. 9. These continued until 4.29 ; afterwards, intervals 

 of rest, at first of fifteen seconds and later of longer duration, separated the convulsions, 

 which also became more severe in type. The animal was finally killed with the anaes- 

 thetic. The convulsions on the left side were identical in character with those observed 

 in other experiments with the cerebrum intact. No convulsions and no movements 

 occurred on the right side. Some slight movements were recorded from this side in 

 the earlier convulsions (see fig. 9), but these were found to be transmitted from the 

 left side. When the shoulders were steadied, no movement was recorded on the 

 right side and no contractions were felt. In view of the fact that convulsions may 

 readily be produced by tutin after removal of both cerebral hemispheres, the absence 

 of convulsions on the left side in this experiment can only be explained by assuming 

 a greater susceptibility on the part of the lower centres affected by tutin to anaesthetics. 

 This susceptibility has been shown to exist (p. 302). 



