316 C. F. MARSHALL. 



In the case of the last abdominal ganglion there are two nerves on 

 each side passing to the telson, corresponding to the two divisions of 

 the nerves to the other abdominal appendages. There is another 

 nerve on each side passing to the skin corresponding to those from 

 the other abdominal ganglia, but differing from them in being placed 

 anterior to the nerves to the appendage. There are also several nerves 

 arising from the posterior end of the ganglion. 



B. Physiology. 



All experiments were performed on the lobster immediately after 

 removal from the tanks. A " holder " consisting of a vertical block of 

 wood fixed in the centre of a board was employed, on which the animal 

 was secured by means of pieces of tape attached to screws placed in 

 convenient positions. The chief difficulty experienced was the rapidity 

 with which the nerves when exposed lose their power of transmitting 

 the nervous impulse, the protoplasm of the nerve appearing to disin- 

 tegrate very rapidly. Another difficulty was the presence of the large 

 quantity of blood pouring out of the wounds which rapidly coagulated 

 and so hindered the operations. 



The first difficulty was overcome after some practice by opening the 

 limbs and exposing the nerves as rapidly as possible. Also by opening 

 the thorax and letting out some of the blood, the amount pouring out 

 of the limbs was much diminished. For purposes of stimulation, a 

 Du Bois Keymond Induction coil with Magnetic Interrupter and a 

 single Daniell Cell were used. The electrodes used were of Platinum 

 wire. In most cases silk ligatures were used for the purpose of lift- 

 ing the nerves on to the electrodes. 



I found very little trouble from the animal's claws, because from 

 their great weight they cannot be moved quickly when out of water. 



1. Experiments on the Nerves in the Large Chelae. 



The chief experiments on the investigation of motor and sensory 

 roots were performed on the nerves of the large chelae, since from 

 their large size they are most suitable for experiment. The nerves 

 are most easily exposed on the ventral surface of the third joint of the 

 limb, where they lie close to the anterior border. The animal in these 

 experiments was in the supine position. 



Experiment A. — The small nerve being intact, the large nerve was 

 ligatured and cut. On stimulating the distal end of the latter nerve 



