SANGUIFEROUS SYSTEM. 44? 



classes. A second pair of vessels originate from the sides of 

 the prolonged arterial median trunk in the head, and a third 

 smaller pair are given off from the same vessel, as shown by 

 Straus and Meckel, near the mouth, which supply the neigh- 

 bouring parts. The oesophageal ring, which also sends for- 

 wards small branches, is formed as usual by lateral branches 

 extending from the anterior part of the aorta to the median 

 subgastric or epi-neural vein ; and this vein continues back- 

 wards, as in other articulata, along the upper surface of 

 the nervous columns to the posterior extremity of the body. 

 This small soft, pellucid vein, lying loosely on the motor co- 

 lumns which I have above described, and from which it is 

 easily lifted, appears to have been mistaken here, as also 

 in the arachnida, for a nervous filament imagined to have 

 some connection with the sympathetic system, or with the 

 function of respiration. It is extensively connected by 

 branches with the peripheral inusculo-cutaneous parts, with 

 the large, tortuous, ramose tracheae, and with the reticulate 

 peritoneal covering of the alimentary canal, but has no 

 resemblance to a nervous filament, in form, texture, or 

 mode of distribution. The elongated and simple form 

 of the heart in the myriapods, and the whole condition 

 of their circulating system appear thus, like the other 

 organs of their body, to be. more closely allied to those of 

 the inferior annelides, and of the larvae of insects, than 

 to the highest adult forms of the latter animals, as supposed 

 by Meckel. 



The sanguiferous system of insects, like their nervous sys- 

 tem, and most other parts of their economy, not only under- 

 goes important changes during the growth and metamor- 

 phoses of these animals, but also presents various forms 

 and conditions of development in the adult state of the 

 different orders of this class. From the opacity of the inte- 

 guments in adult insects, and the limited distribution of 

 blood vessels through their highly aerated body, the course 

 and extent of their circulating system were long concealed 

 from observers, and the dorsal vessel was early believed to be 

 a glandular sac shut at both ends, and destined, by its con- 

 tinued peristaltic action on a contained honey-like substance, 

 to form the abundant fatty matter of their body. By examin- 

 ing, however, minute transparent larvae under the micros- 



