29? 



nerve corresponding to the pneumo-gastric, or par vagum, and shows 

 that it is distributed chiefly to the organs of digestion and the respi- 

 ratory passages. He next describes the anterior lateral cephalic 

 ganglia, which, from their position, might be regarded as auxiliary 

 brains. The situation and course of another nervous tract, which 

 from its extensive connexions and peculiar mode of distribution is 

 considered as corresponding to the sympathetic system, are also 

 traced. The author notices a set of nerves which, adopting the views 

 of Sir Charles Bell, he considers as analogous to those which the lat- 

 ter has denominated the respiratory nerves of vertebrated animals ; 

 and among a great number of interesting observations, of which it is 

 impossible to give any abridged account, one of the most remarkable 

 is the discovery that the primary longitudinal nervous cords of in- 

 sects consist of two tracts, the one situated over the other, corre- 

 sponding to the two columns of which the spinal cord consists in ver- 

 tebrated animals ; the one appropriated to sensation, and the other to 

 voluntary motion ; the nerves from each of these tracts being variously 

 combined, according to the purposes they are designed to fulfil. This 

 important distinction, which was first traced in the nervous cords 

 of the Lobster, was afterwards distinctly observed by him in the 

 Scorpion and the Scolopendra, and lastly, in several species of insects, 

 as the Gryllus viridissimus, the Curabus, the Papilio urticce, and the 

 Sphinx ligustri. Numerous drawings of the parts described accom- 

 pany the paper. 



3. " Observations on the Torpedo, with an account of some addi- 

 tional experiments on its Electricity." By John Davy, M.D., F.R.3., 

 Assistant Inspector of Army Hospitals. 



The first part of this paper is occupied by an investigation of the 

 circumstances attending the fcetal development of the Torpedo. In 

 the first stage of embryonic growth which the author had an oppor- 

 tunity of observing, when the embryo was about seven tenths of an 

 inch in length, it had neither fins nor electrical organs, nor any ap- 

 pearance of eyes ; it. exhibited short external branchial filaments, not 

 yet carrying red blood : and there was a red spot in the situation of 

 the heart, communicating by red vessels in the umbilical cord with the 

 vascular part of the egg. There is no membrane investing the foetus, 

 as is the case with some species of Squali ; nor any fluid in the uterine 

 cavity ; neither could the author find any urea or lithic acid in that 

 cavity. By taking the mean of many observations, it appeared that 

 the weight of the egg, before any appearance of the embryo, is 1 82 grs., 

 and after its appearance, including the weight of the latter, 177 grs.; 

 while the weight of the mature fish is about 479 grs. ; showing an 

 augmentation of more than double. Thus it differs remarkably, in this 

 respect, from the fcetal chick, which at its full time weighs consider- 

 ably less than the original yolk and white from which it is formed. 

 No communication can be traced between the foetus of the Torpedo 

 and the parent, through the medium of any vascular or cellular struc- 

 ture ; and the stomach of the former is always found empty. Hence the 

 only apparent source of nourishment is absorption from the surface 5 



