III. THE ORGANS OF THE BODY. 



A. Organs of the Vegetative Group. 



1. Circulatory Apparatus. 

 220. 



As we have already considered the blood and lymphatic vessels in the 

 second part of our work ( 201-211), we shall here be engaged merely 

 with gleanings from what has been previously referred to. Thus we have 

 to describe the heart, the lymphatio glands and lymphatic, organs, with 

 the spleen, as well as the remainder of the so-called blood-vascular glands. 



The heart the muscular central organ of the circulatory system 

 consists of the pericardium, a serons sac (which has been previously 

 referred to, p. 226) of muscle, and of the so-called endocardium. The 

 latter is analogous to the T. intima of larger vessels ( 204), while the fleshy 

 mass of the organ corresponds to the mus- 

 cular layers of the latter. Many modifi- 

 cations, however, are apparent. 



The pericardium corresponds in its 

 texture to many of the true serous sacs. 

 It presents for consideration a thick pari- 

 etal and thin visceral portion. The latter 

 is connected with the fleshy mass of the 

 organ by means of that connective-tissue 

 known as subserous, and shows espe- 

 cially in the grooves of the heart, but at 

 times also over nearly its whole surface, 

 collections of fat cells (p. 198). 



The vessels of this structure have 

 nothing special about them, and the nerves 

 of the parietal layer are supplied, accord- 

 to Luschka, by the right vagus (ramus 

 recurrens) and phrenic. The epithelium 

 has beeri already dealt with at p. 139, 

 and the fluid contents of the sac at p. 

 230. 



We have likewise considered the stri- 

 ated muscle of this involuntarily acting organ while speaking of muscle 

 generally at p. 292. 



The connection of the reticularly united muscular fibres one with 

 another (fig. 397) is very peculiar. They are not, as in other striped 



y p'Tjipj Moggr^ 



Fig. 397. Muscle-fibres from the heart, 

 after Schweigger Seidel. To the right the 

 boundaries of the cells and the nuclei 

 are to be seen. 



