Medicinal Leech. 133 



prevents us from seeing- this structure in this Prepai-ation. It is 

 figured, however, by Brandt, its discoverer, Tab. xxix. B, 7 d. e., 

 where it is seen not to be distinctly prolonged upwards into con- 

 nection with the stomato-g-astrie or supra-oesophageal ganglia. 

 Its relation would appear to correspond to the nervus recurrens 

 of Arthropoda, but that it is in relation with the ventral rather 

 than with the dorsal aspect of the digestive tube. 



For the ' intermediary nerve,' see the memoir of Faivre, its dis- 

 coverer, in the Ann. Sci. Nat. Ser. iv., tom. vi., p. 29. In this 

 author's previous memoir, published in the volume of the 

 Annales des Sciences Naturelles, immediately preceding the 

 one just referred to, will be found, at p. 361, an account 

 of the various chemical reagents which may be employed in 

 the microscopic investigation of the nervous system of An- 

 nelids. For methods of preparation of entire specimens for 

 the dissection under a lens, without which much of what 

 is here described cannot be made out by the student for 

 himself, see Leydig, Vergleich. Anatomic, pp. 164, 165; and 

 Gratiolet, Ann. Sci. Nat. iv. 17, pp. 177, 178, iSi. 



For the lateral ganglia in apposition with the ventral ganglia, see 

 Leydig, Vergl. Anat., Taf. ii., fig. 3 e. 



For the lateral ganglia developed upon the inferior pair of nerves, 

 see Leydig I. c, p. 146 ; Quatrefages, Histoire Naturelle des 

 Annales, tom. i., p. 81, pi. iii,, fig. i, i. k., Nereis regia. 



42. Medicinal Leech (Hiruclo Medicinalis), 



Dissected so as to show its reproductive and segmental organs in sita, the digestive 

 and pseud-haemal systems having been in great part removed, and the integuments 

 fastened out on either side. 



At about the point of junction of the first with the second sixth 

 of the body's length, is seen a globular body partly overhanging 

 and partly projecting to the left of the nerve cord, communicating 

 mesially with a siphon-shaped muscular tube, and receiving on 

 either side two tubes of smaller cali])rc but similar structure. The 

 globular organ is constituted partly ]>y muscular and i)iirtly by 



