484 



GLAND. 



adjoining figure (fig. 214) conveys a very 

 accurate representation of this structure as it 

 exists in the biliary organs of the astacus 

 jftuviatilis, the digital tubuli (r) being depicted 

 as they appear when partly unravelled. 



In another of the Crustaceans, pagurm stria- 

 tus (fg. 215), the same kind of structure is 



Fig. 215. 



observed, constituting a very complex liver. 

 In the suuilla mantis that organ is so remark- 

 ably intricate that Cuvier supposed it formed 

 an exception when compared with the other 

 genera of the Crustacea, which, as we have 

 seen in the instances above, possess biliary 

 organs composed of blind tubes, by being lo- 

 bulated and solid like a conglomerate gland.* 

 It has, however, been ascertained that the 

 lobules are excavated in their whole extent, 

 and communicate by openings with the intes- 

 tine, which runs through their sponey mass, 

 so that the secreting surface is wonderfully 

 increased in extent.f 



That the liver consists of a blind pouch, 

 originating from the intestinal canal and be- 

 coming more and more complicated, is further 

 shown in many of the Mollusca, in which the 

 excretory ducts are so large that they appear 

 like branches of the intestine, and thus present 

 a structure which is somewhat analogous to 



* Lemons d'An. Comp. t. 4. p. 152. It is proper 

 to observe that Cuvier, in thus alluding to a solid 

 conglomerate gland, appears to have fallen into 

 the common error respecting; the nature of the 

 minute granules, or acini as they are called. 



t Mullcr de Gland. Secernent. Struct, p. 70, 

 $5. 



those curious ccecal diverticula observed in 

 certain of the Annelida, well seen in the 

 ap/trodita aculeata, and which are by some 

 anatomists regarded as forming a rudimentary 

 liver. 



The evolution of the liver in the embryo 

 affords an additional proof of the disposition 

 of the secreting surface or membrane in the 

 interior of the compound glands. In one of 

 the Gasteropoda. ( Limnaus stagnalis) the liver 

 is first produced as a pellucid sac from the 

 intestine. In an amphibious animal (buj'o 

 cainpanisonus) a prolongation in the form of 

 a sac is seen in the intestinal membrane, which 

 constitutes the first appearance of the liver; as 

 the development proceeds, the hepatic duct is 

 formed, and becoming ramified, produces at 

 length a number of branching tubes, which 

 present a granulated form. The evolution of 

 the liver in the green lizard (lacerta viridis) 

 is very similar, the organ first appearing under 

 the form of a hollow sac proceeding from and 

 communicating with the cavity of the intestine, 

 and subsequently having branches of ramified 

 tubes added.* 



If from the investigation of these more simple 

 forms, which might be multiplied almost ad in- 

 fotitum, we proceed to the conglomerate glands 

 of Mammalia, it will be observed that, al- 

 though the component parts of these highly 

 organized bodies are so closely packed together 

 as to present a solid and granular appearance, 

 yet by a careful inspection it may be satisfac- 

 torily determined that the true secreting struc- 

 ture consists of tubuli with ccecal ends. For 

 this purpose the testicle may be advantageously 

 selected : if this organ without any previous 

 injection be divided, the section at first sight 

 seems to consist of a great number of small 

 roundish bodies or granules; but if, as occa- 

 sionally happens, the tubes are distended with 

 semen at the time of death, by a more cautious 

 examination it is immediately apparent that 

 these little bodies are composed of a very fine 

 tube coiled up or convoluted. By injecting 

 the tubuli seminiferi with mercury, the formation 

 of the little grains is rendered more evident ; 

 but the most successful mode of displaying 

 the whole internal formation of the testis is by 

 filling the tubuli with a coloured size injec- 

 tion, f 



It was remarked by FerreinJ that the kid- 

 ney is a tubular organ, and the extensive re- 

 searches of Miiller as well as those of Huschke 

 have proved that the secreting or cortical part 

 is made up of an immense number of serpen- 

 tine tubes of an equal diameter throughout, 

 ending in blind sacs, and becoming continuous 

 with the straight canals placed in the cones of the 

 organ. This structure is seen \njig.2l6, where a 

 magnified view of the cortical ducts of Ferrein, 

 the secerning apparatus, and the straight excre- 

 tory tubes is given as the parts exist in the 

 scijirus. This structure offers a close resem- 

 blance to the tubuliform liver of some insects. 



* Miiller 1. c. tab. x. fig. 13. 



t Sir A. Cooper on Testicle. 



f Mein. de 1'Acad. Roy. des Sc. 1749, p. 489. 



