XX11 INTRODUCTION. 



Class 2. The Arachnida, yields 

 TEGENERIA MEDICINALIS, the Spider. The No. 20 of this work. 



Class 3. The Insecta, yields 



CANTHARIS VESICATORIA, the Spanish Fly. The No. 5 of 

 this work. 



APIS MELLIFICA, the Honey-bee. The No. 6 of this work. 



Coccus CACTI, the Cochineal insect. The No. 10 of this work. 



CYNIPS QUERCUS FOLII, the Gall insect. The No. 15 of 

 this work. 



Class 5. The Annelida, yields 



SANGUISUGA, Blood-sucking Leeches. The No. 17 of this 

 work. 



ANNELIDA TERRICOLA, Earth-worms. The No. 23 of this 

 work, not considered officinal. 



II. Division. HETEROGANGLIATA. 



The characters of this division are well defined, and the 

 irregular and unsym metrical forms of the bodies of most of the 

 genera which compose it, in exact relation with the arrange- 

 ment of the nervous apparatus. 



As in the Articulata, there is a large nervous mass placed 

 above the oesophagus, which supplies the principal organs of 

 sense, but the other ganglia are variously dispersed through 

 the body, although always brought into communication 

 with the supra-cesophageal portion by connecting filaments. 

 Throughout all the forms is found a distinct relation between 

 the size and development of the nervous centres and the per- 

 fection of the animal, indicated by the senses and organs of 

 motion with which it is provided. 



Three classes of this division furnish each an animal sub- 

 stance yielding a medicinal agent. 



Class 1. The Cephalopoda, yields 

 SEPIA OFFICINALIS, the Cuttle-fish. The No. 18 of this work. 



Class 3. The Gasteropoda, yields 

 HELIX POMATIA, the Snail. The No. 19 of this work. 



Class 4. The Conchifera, yields 



OSTREA EDULIS, the common Edible Oyster. The No. 14 of 

 this work. 



