1894.] of the Nervous System of the Embryonic Lobster. 413 



tion than that here the nervous stimulus passes from one element to 

 the other. It appears to me to be at least worth while to throw out 

 the suggestion that the nervous energy resembles a static electrical 

 charge, in the fact that the discharge takes place most readily through 

 points. Wherever nerve endings have been demonstrated, the break- 

 ing up into finer and finer branches, which end freely, has been shown 

 to take place. 



On the view suggested, each nerve element resembles an electrical 

 condenser capable of charging itself, and being suddenly discharged 

 by an appropriate stimulus. It is interesting to note what would 

 happen upon some such theory as this, supposing one of the elements 

 D to be stimulated in any way. Imagine, for instance, the element 

 D Thorax IX to be caused to discharge, either by an impulse from a 

 sensory nerve, or from the brain. The main discharge would, we 

 must suppose, pass into one of the motor elements such as E, by means 

 of the fine branches which both send to the neuropile, and the muscle 

 innervated by that particular fibre would be stimulated. A portion 

 of the charge would, however, pass to the lateral and terminal tufts 

 of D Thorax IX, and we may suppose that in this way D Thorax VIII 

 and D Thorax X are made to discharge, as well as C Thorax VI. If 

 we suppose the C elements to influence some other motor element in 

 the neuropile, say F, then it will be seen by following out the result 

 in the figure, that all the E and F elements upon one side of the 

 thorax would be stimulated by the single stimulus to D Thorax IX. 



"With regard to elements of the class A, which start from a cell in 

 one of the anterior ganglia and send a fibre down the cord, the fact 

 that they give off collateral branches to the nenropile of each gan- 

 glion would seem to indicate that they in some way control an 

 element, which also sends branches into that particular ganglion, 

 and the suggestion would be that by their means a series of elements 

 are stimulated all along the body by an impulse from the brain. On 

 the other hand, by means of elements B, a particular ganglion would 

 be placed in direct communication with the brain. This communica- 

 tion would be independent or correlated with a stimulus to (or from) 

 all the ganglia through which the fibre passes, according to whether 

 the absence of collaterals is the true condition of the element, or is 

 due merely to imperfect staining. 



A similar consideration will apply to the giant fibres (A(a)Br). 

 It has been already stated that no collaterals have ever been observed 

 on these fibres. According to Betzius branches go directly from their 

 ends to the nerves of the last abdominal ganglion, and it, therefore, 

 seems probable that they serve the purpose of putting some organ into 

 direct communication with the brain. The most obvious suggestion 

 would be that it is by their means that the muscles of the tail-fin, the 

 steering apparatus of the animal, are controlled by the brain. There 



