Miscellaneous, 79 



without distinct nervous fibres. In the space between each pair of 

 connectives is a very delicate nervous bundle, apparently of the same 

 substance as the connectives : this represents the intermediate nerve 

 described by E. Faivre in the common Leech. 



The suboesophageal inflation is of large size as compared with the 

 other ganglia ; it is somewhat triangular in form ; its truncated apex 

 is continuous with the ganglionic chains ; its concave base embraces 

 the lower surface of the oesophagus ; and its antero-lateral angles are 

 continuous with the cerebral connectives. 



On the margins of this fibro-nervous mass is arranged a series of 

 capsules or inflations, formed of unipolar cells perfectly similar to 

 those of the ventral ganglia ; in the median line there is also a double 

 series of eight or ten similar capsules. By counting these capsules, 

 we find that, as each simple ganglion contains six of them, the sub- 

 oesophageal ganglion is formed by the union of at least four ganglia, 

 which are confounded together by the extreme shortness of their 

 connectives. The caudal inflation presents a very similar arrange- 

 ment of parts ; by the same mode of calculation it appears to result 

 from the fusion of at least seven ganglia. 



The cerebrum exhibits nothing to differentiate it from the other 

 ganglia : it consists of a fibro-nervous loop continuous with the con- 

 nectives and passing over the oesophagus, and bearing on its margin 

 on each side six capsules containing unipolar cells. From their 

 direction a certain number of fibres originating from these cells seem 

 to bear towards the median line, and to pass from one side to the 

 other. Thus the cerebrum may be regarded as consisting of two 

 simple ganglia. 



The lateral nerves (two in number) originate from each side of 

 their ganglion ; at their origin they are united in a common sheath 

 of fibro-elastic tissue, but they soon separate. After a short course 

 (about 1 millim.) the anterior branch usually presents on one side a 

 small ganglionic inflation, often exceeding -ji^ millim. in size; this, 

 which is sometimes fusiform, sometimes quadrangular, consists of a 

 granular material, in which is a large oval nucleus, usually furnished 

 with several nucleoli. It commonly gives off a short branch, which 

 unites the anterior with the posterior root ; when the inflation is 

 quadrangular, each of its angles emits a nervous branch. 



Another very interesting peculiarity consists in the existence of 

 nervous cells appended here and there, like grapes, to the most deli- 

 cate extremities of the lateral nerves. These cells, which are usually 

 unipolar, measure from yfu to -^^ millim. ; they contain a granular 

 matter enclosing an oval nucleus with one or more nucleoli. 



As to the signification of these cells, the author says : "Brandt 

 indicated in the Leech a gastric system, which other skilful observers 

 were subsequently unable to discover. In 1857, Faivre discovered 

 in the stomachal membrane of the Leech a network formed of ner- 

 vous tubes and cells — a network the existence of which is certain, 

 but of which he could not ascertain the connexions. Now, from the 

 facts that I have ascertained with regard to Clepsine, I am convinced 

 that this nervous network is formed at the expense of the terminal 



