4G0 



THE INSECTA. 



$339. 



whether one of the pairs of these glands with these Hemiptera, may not be 

 a poison apparatus. 



The Insecta have no distinct Hepatic Organs, but the function of a Liver 

 is performed by the walls of the stomach, the internal tunic of which is 

 composed of closely-aggregated hepatic cells. With many species whose 

 stomach has caecal appendages, the walls of these last have a similar hepatic 

 structure, and must secrete, therefore, a bile-like fluid.^^'^' 



With some Insecta, the ileum has glandular appendages, whose product 

 is perhaps analogous to a pancreatic fluid. The two or four rows of fol- 

 licles which, as before mentioned, are situated on the ileum of the Penta- 

 tomidae and some Coreidae, would, in the same manner, be regarded as a 

 Pancreas. The same remark applies to the ramified appendages, which, 

 with Gryllotalpa, open into the stomach below the two caeca, as well, also, as 

 to the two or three follicles which, with Pyrrhocoris, are inserted, laterally, 

 on the posterior part of the ileum. ^^''^ 



There is found, with all Insecta, a Corpus adiposiim, — a tissue, composed 

 of adipose cells, which is intimately connected with the functions of digestion, 

 and assimilation. This body is especially developed towards the end of 

 the larval state,' and it disappears, for the most part, during the pupa 

 period, so that only a few traces of it are found with Insecta in their per- 

 fect state. It is usually of a white, or a dirty -yellow color, but is also 

 observed of a green, red, or orange hue. In the larvae, the fat ceils gen- 

 erally form pretty large, lamelliforni lobes, sometimes ramified or reticu- 

 lated, sometimes plicated, spread through the abdominal cavity in all the 

 intervals of the viscera. These lobes are always traversed and retained 

 in place by numerous trachean branches. With the perfect Insecta, the 

 remains of this body are not usually found except in. the posterior portion 

 of the abdominal cavity, where they consist of fat-cells loosely scattered, 

 and not retained by the tracheae.^-"* 



18 For these biliary orgjans, see J. Müller^ De 

 Gland, struct, p. 67. The Malpighian vessels 

 which were formerly regarded as biliary tubes, 

 will be treated of in future (§ 346).* 



ly See L. Dufour, Ilecherch. sur les Orthopt. p. 

 332, n. II. fig. 19 {Gryllotalpa), and Recherch. 



sur les Hi^miptöres, p. 44, PI. II. fig. 19, 21 {Pyr- 



rhocoris).\ 



-"O See L. Dufour, Recherch. sur les Carabiq.,in 

 the Ann. d. Sc.' Nat. VIII. 1826, p. 29 ; Recherch. 

 sur les Ilemipt. p. 141, and Recherch. sur les 

 Orthopt. p. 291, 385, 562.]: 



* [ ^ 339, note 18.] The liver of the Insecta, as 

 well as that of the luvertebrata generally, has been 

 investigated by irill (Mu/ler's Arch. 1848, p. 502) 

 who has applied the same chemical mode of in- 

 <(uiry, as that of Brugriatelli and fVurzer upon 

 the Malpighian vessels showing their urinary char- 

 acter (see infra § 345, note 2). With the Insecta, 

 lie regards as hepatic the caecal and other glandu- 

 lar aijpendages which, when present, lie upon the 

 so-called l^entriculuK, thus confirming the suppo- 

 sition expressed in the foregoing note. For the in- 

 timate microscopic structure of the liver of the In- 

 secta, see Leidy, Amer. Jour. Med. Sc. XV. 1848, 

 p. 1. — En. 



t [ § 339, note 19.] For the hepatic organs of 

 fle/ontoma, see Leidy, loc. cit. p. 63, 1*1. X. fig. 

 4, i. They consist of four long very tortuous tubes 



closely applied to the intestinum tenue ; they join 

 the intestine at the junction of the duodenum and 

 ileum. — Ed. 



J [ § 339, note 20.] See, upon the Corpus adi- 

 posum, Mayer (Ueber die Entwickelung. des Fet- 

 tkörpers, &c. bei den Lepidopteren, in Siebold 

 and Kölliker's Zeitsch. I. p. 175) who has traced 

 its development. 



These adipose bodies are formed from a great 

 number of separate, flattened, usually many- 

 pointed lobes. These lobes consist of pouches with 

 structureless walls, and filled with fal-gl<ibules. 

 Each jiouch is originally a simple cell with a large 

 nucleus attached to its wall. In this cell are 

 formed daughter-cells, which, when filled with fat, 

 burst, and thereby the mother-cell becomes the lab» 

 containing sac. — Eu. 



