384 BIOLOGY. 



the intestinal system divides, when it is repeated in the 

 after-animal, or in the sphere of animal life. The gus- 

 tatory organ is the nerve-intestine ; the prehensile organ 

 the bone-intestine ; the organ of deglutition the muscular 

 intestine ; while the poison -organ is the proper cephalic 

 intestine, or the stomach. 



2. VASCULAR ORGANS. 



2194. The vascular system regarded " en masse/' or 

 in a general sense, has to participate in the nutrition of 

 the body ; so far it takes the place of the cellular tissue, 

 and cannot therefore be developed for itself into any 

 special organs. If, however, certain vessels separate 

 from the general system, and combine with other systems 

 unto the performance of special offices or functions, 

 organs then originate, which, nevertheless, do not, in a 

 rigid point of view, belong to these systems. 



2195. There are therefore as many vascular organs as 

 there are possible combinations ; thus with the tegu- 

 ment, the lung, the intestine, the sexual parts, and with 

 the systems of animal life. 



a. CUTANEO-VASCULAR ORGANS BRANCH!^. 



2196. The development of the vessels unto a special 

 organ in the integument are Respiratory organs; or, 

 more properly speaking, the development of the integu- 

 ment to constitute a special organ in combination with 

 the vessels, is a respiratory organ. 



2197. In the commencement the branchiae are only a 

 vascular network upon, and therefore subordinate to, the 

 integument. They pass, however, through all possible 

 stages of development, until they have subjected and 

 converted also the integument into a vascular system ; a 

 point which is attained in the formation of the lungs. 



2198. The branchial membrane already commences 

 in the earthworm to concentrate itself and dilate, so as 

 to form what have been called the sacculi or pouches ; in 

 the leech it is folded inwards, so as to form lateral 

 vesicles or cysts, that prognosticate the air-passages or 



