122 
DR. C. H. JONES ON THE STRUCTURE 
An important circumstance which cannot but arrest the attention in examining 
the livers of many fishes, especially those of the Skate and Cod, is the very large 
amount of oily matter which is manifestly in a free state ; this, as we have on former 
occasions remarked, indicates a low intensity of the respiratory process, and also 
serves as a further proof of the correctness of the view here taken of the structure of 
the liver ; for were this abundant oily matter free in the cavities of ducts, it should 
surely constitute in great part the contents of the gall-bladder, and so marked a 
difference would not exist between the dark-green fluid found in that receptacle, and 
the dead white of the adjacent parenchyma of the liver. Doubtless the excretory 
ducts separate, by a process of vital absorption, the bile from the oily matter in which 
they are bathed. 
Among Reptiles I have examined the Common Snake {Coluber natrix), the Fresh- 
water Tortoise {Emys europced), the Turtle {Chelonia my das) ^ the Newt {Triton crista- 
tus), the Frog {Rana temporaria) and the Toad {Bufo vulgaris) ; in all these the liver 
is, Kar e^oyjiv, a Solid gland, the capillary network extending equally in every direction : 
the coats of the capillaries are remarkably strong, and there can be no better oppor- 
tunity than is here presented for examining their structure, which corresponds pretty 
closely with that figured by Henle. In most of these animals I have examined the 
ducts by dissecting them out in the way! have described, but by no means with such 
satisfactory results as I have obtained in fishes ; this depends on the greater strength 
of the fibrous and other tissues composing the framework of the gland ; however, in 
the Newt, Snake and Toad, I have been able to determine sufficient respecting the 
ducts, to satisfy me that they do not differ in any essential circumstance of structure or 
arrangement from those of fishes : thus it is quite certain that they bear only a small 
proportion to the mass of secreting parenchyma ; they can be traced running a long 
course through it, and giving off very few branches, and in one or two instances they 
have clearly been seen to terminate by closed extremities. In structure they consist 
of a delicate epithelium with an investing layer of basement membrane, and often of 
fibrous tissue ; these latter elements are often wanting in the smaller ducts, whose 
diameter varies from 3 to looo th of an inch ; towards their terminal extremity also the 
tubular character is often completely lost, and the nuclei become indistinct, so that 
there remains only a tract of granulo-amorphous matter containing some minute oil- 
drops, which is soon lost in the surrounding parenchyma. This mode of termination 
in reptiles, as well as in fishes, is manifestly equivalent to terminating by a closed 
caecal extremity, as far as regards a direct communication with the secreting paren- 
chyma. 
In none of the Reptilia that I have examined has there appeared any manifest 
tendency to a division of the parenchyma into lobules ; it consists of delicate cells, 
free nuclei and granular, with a small proportion of oily matter : in the Snake these 
are arranged into masses of a definite form, which are disposed so as to represent 
short linear series coalescing to form a plexus, but in the others they merely occupy 
