491 



LIZARD. 



LLAMA. 



4 S3 



hepatic columns. At other times free terminations of the hepatic 

 columns are apparently developed for a considerable period, perhaps 

 until the whole organ has nearly arrived at perfection, their formation 

 appearing to precede by some time that of new anastomoses, as ia the 

 case in the chick and other birds, and, according to J. Miiller, in a 

 few mammals ; in the latter of which, according to Muller's figures, 

 the hepatic columns are grouped in lobes. These free superficial 

 hepatic columns may perhaps throw some light upon the meaning of 

 Weber's and Krause's statements respecting the biliary ducts with 

 ccecal ends upon the surface of the liver. With regard to the biliary 

 ducts they are nothing but secondary excavations of a part of the 

 primarily solid hepatic columns and of the larger internal tracts, which 

 border upon the original epithelial diverticulum, and which all con- 

 sist of many series of cells. The excavation commences iu the 

 common biliary duct, proceeds towards its branches, and must be con- 

 sidered to take place exactly as in other glands, namely, either by 

 solution of the inner cells of the rudimentary structures, or by the 

 excretion of a fluid between them, and the consequent production of a 

 cavity. In this mode of regarding the matter, there is only one point 

 for consideration, namely, that according to Remafc all the hepatic 

 columns, even the largest, form anastomoses, whilst, as is well known, 

 the biliary ducts ramify without anastomosing. The only solution of 

 this difficulty consists in assuming that the anastomoses of the primary 

 largest hepatic columns do not continue in the course of the further 

 development, but that they are re-absorbed, a process which has 

 its analogue in many phenomena of foetal growth. In man alone 

 might we find au exception, for it seems that the anastomoses of the 

 right and left hepatic duct, in the fossa hepatis, described by E. H. 

 Weber, are perfectly well explained by Remak's observations, and 

 are simply the embryonic anastomoses of the rudiments of these 

 canals, which have attained to some though no very great develop- 

 ment. The mode of origin of the fibrous membranes of the biliary 

 ducts becomes readily comprehensible, if we reflect how the net-works 

 of hepatic columns and the fibrous layers of the liver interdigitate ; 

 so that layers of connective tissue, &c., might be readily formed 

 around the hepatic cylinders from those elements of the fibrous layer 

 which are nearest to them. The further development of the vessels, 

 nerves, Ac., presents no difficulties, taking place in the same way as 

 in other organs. The gall-bladder in the chick, according to Remak, 

 is a process at first solid, of one hepatic duct, which subsequently 

 becomes hollow and rapidly increases in size. I saw the folds of its 

 mucous membrane as early as in the fifth month in a human foetus. 

 The investigation of the liver is best undertaken in the pig, in which 

 animal the distinct demarcation of the lobules greatly facilitates the 

 comprehension of the relations of the secreting parenchyma to the 

 vessels and hepatic ducts. The hepatic cells may be isolated with 

 the greatest ease in all animals, either singly in series or in reticulated 

 fragments; but to comprehend rightly their collective arrangement, no 

 better means exist than the making of fine sections in a fresh liver with 

 the double knife, for which sections made off hand with a razor, even 

 in a liver previously hardened in alcohol, pyroligneous acid, chromic 

 acid, &c., are by no means sufficient substitutes. We do not mean to 

 say that the hepatic cell net-work cannot be seen at all in this manner, 

 for it is visible even in opaque sections of liver by reflected light, but 

 merely that no complete view can thus be obtained. The finest 

 hepatic ducts are not readily found, though a careful search in nearly 

 all sections, which include many lobules, will almost certainly detect 

 scattered fragments of them, readily distinguishable by their small 

 polygonal cells, at the edges of the lobules, and long examinations 

 may perhaps eventually discover such a fragment in connection with 

 the hepatic cell net-work, which however I have not yet succeeded in 

 doing. The coarser biliary ducts present no difficulties. Their glands 

 are seen readily, partly with the naked eye, partly by the use of dilute 

 caustic soda. Weber's anastomoses of the two hepatic ducts in the 

 fossa transversa are visible in good injections. The vasa aberrantia in 

 the left triangular ligament and in other localities are readily per- 

 ceived even without injection on the addition of acetic acid or of 

 caustic soda. The nerves and lymphatics of the liver are, except their 

 finest portions, easily seen in man. The blood-vessels require good 

 injections, for which purpose, in the human subject, I especially 

 recommend children's livers, in which the distribution of the arteria 

 bepatica in the serous coat, on the vessels, &c., is beautifully distinct. 

 The capillary net-work of the lobes may readily be filled with fine 

 injection, and a series of excellent preparations of this kind by various 

 masters of the art are everywhere to be met with." 



(Valentin, Text-Book of Physiology ; Carpenter, Manual of Human 

 Physiolor/t/ ; Kolliker, Manual of Human flittoloyy.) 



LIZARD. [SAURIA.] 



LIZARD-SLEKER, a name given to the species of Samothcra, a 

 genus of Birds. [CuccLtDJS.] 



LLAMA (Auchenia of Illiger; Lama of Cuvicr and others), the 

 generic name for that form of the Camelidce which is confined to the 

 New World. Dentition : 



2 i i 



Incisors, _ ; Canines, ; Molars, 



6 1 1 



44 



= 30. 



The difference between the dentition of the two sub-families of 

 Candidas, Camdiu and Auchenia, appears to consist mainly in the 

 HAT. HIST. DIV. vou III. 



absence of the two small pointed teeth, which are found in the interval 

 or ' bar ' between the canines and the molars in the Camels, from the 

 jaws of the Llamas. Thus the Llamas have four false molars, as they 

 may be termed, less than the Camels. In other respects the dentition 

 of the one is, as nearly as may be, the dentition of the other. The 

 following cut exhibits the dental arrangement of the Dromedary, and 

 will convey a sufficiently accurate idea of the same parts in the Llamas, 

 if the spectator will suppose the absence of the four teeth above 

 mentioned. The difference was considered by F. Cuvier to be of 

 such small importance that he has not considered it necessary to give 

 a figure of the dentition of Auchenia. 



Teeth of Dromedary, f. Cuvier. 



Baron Cuvier observes, that the Camels and Llamas differ in many 

 points from the Horned Ruminants. Considered as a whole, the head 

 of the former presents a narrower and more lengthened muzzle (un 

 museau plus aminci), a cranium larger in proportion, orbits placed 

 more forward, and the edges of those orbits more prominent, in 

 consequence of the temples being more sunk. 



In the Llama the bones of the nose are short, and their extremity 

 notched ; their base is slightly enlarged ; the lacrymal bone is but 

 little advanced upon the cheek, and leaves a wide space between its 

 anterior angle and the upper external angle of the nasal bone. It does 

 not cover the orbitary part of the maxillary bone, but stops above the 

 suborbital internal hole ; nothing of the vomer is to be seen above 

 the spheno-palatine hole, and a small portion of the pterygoid internal 

 apophysis scarcely shows itself there. The parietal bones are soon 

 united into a single bone much wider than it is long ; the posterior 

 suture of which remains, nevertheless, before the occipital crest. The 

 temporal wing of the posterior sphenoid bone has a descending pro- 

 minence, and its pterygoid wing terminates in a sharp point, which 

 projects more than that of the pterygoid apophysis. The tympanic 

 bones are compressed, but project very much j the occipital crest is 

 well marked. 



The true Camels, according to the same author, have the occipital 

 crest still more marked and the temples still more sunkeu than they 

 are in the Llamas, and almost as much as they are in the Carnassiers. 

 The occipito-temporal suture is very much in front of this crest. The 

 bones of the nose are of much less width at their bases, and there-is a 

 great space between the small membranous portion which exists at 

 their angle and the lachrymal bone, which is extremely small on the 

 cheek ; it does not reach in the orbit even to the eJge of the suborbital 

 internal hole. There is, as iu the Llama, a small membranous space 

 between the lachrymal, frontal, and palatine bones, which advances to 

 that spot by a small tongue-shaped portion. The wing of the vomer 

 shows a small portion above the analogous hole of the spheno-palatine 

 bones. The internal pterygoid apophysis does not exist except towards 

 the point of the wing : it does not rise till it reaches the body of the 

 sphenoid bone, and there is no space between the wing of that bone 

 and the wing of the palatine bone. 



In all other respects, as regards the head, the Camels and Llamas 

 offer a singular resemblance. The sockets of the incisors are smaller 

 than in other Ruminants, and the canal analogous to the pterygo- 



2 I 



