194 THE AMERICAN MONTHLY [September, 



The opening, therefore, is not adventitious. This opening is seen at 

 b. At the junction of our subdivision with the neighboring ones we 

 see another opening, c, with more distinct lining membrane. 



The contents of the subdivision seem, with a low power, to be of a 

 granular nature, separated, or rather penetrated, by fine channels which 

 converge from all parts of the lobule to meet at a common centre at b. 



In one part of the field we see what seems to be a mass of black dots, 

 in no way resembling the other parts of the structure and which have 

 not taken the stain. 



We will now use the higher power and endeavor to make out more 

 closely the nature of the structure we are studying. 



What, with the low power, seemed to be a mass of granular matter 

 is now seen to be composed of pentagonal cells, with large nuclei 

 and one or more nucleoli. (Fig- 2, a and b.) Each cell is separated 

 from its neighbors by the fine channels before referred to. The fissures 

 are seen to be composed of connective tissue. The opening at c (Fig. 

 1) is seen to have a tunica adventitia of .connective tissue and a lin- 

 ing membrane composed apparently of a single layer of epithelial cells. 

 It is clearly separable from the surrounding tissue. 



At b the lining membrane is very delicate and the epithelial cells 

 crowd closely around it, making it appear that in some places the lin- 

 ing membrane is merely the walls of the epithelial cells themselves. 

 We are warranted, from these details, in pronouncing the opening at b 

 to be a vein and the one at c a duct. In other parts of the structure, 

 in the connective tissue between the subdivisions, we see the well-known 

 appearance of an artery cut across and accompanied by a vein and a 

 duct, the artery being the smallest of the three. Let us now sum up. 



We have a whole organ, divided into irregular, generally pentagonal 

 lobules, composed of polygonal epithelial cells, each with its nucleus 

 and one or more nucleoli, the cells being separated from each other by 

 fine inter-cellular channels. Each lobule has a central vein, and in the 

 inter-lobular connective tissue are found artery, vein, and duct. 



This appearance is characteristic of but one organ, viz., that which 

 we call the liver. 



We can safely say, then, that we have to do with the section of a liver, 

 and since the section is that of a whole organ, the liver must be that of 

 a small animal. 



A rough guess at the weight of this liver would put it at one-fourth 

 of an ounce, and, assuming the proportion of the weight of the liver to 

 that of the whole body as one to forty, we might infer that the weight 

 of the animal from which this liver came was about ten ounces. If it 

 be a fact, as Klein states (Elements of Histology) , that in man, carniv- 

 orous animals, and rodents the lobules of the liver are more confused 

 and less distinct than in other animals, we should be justified in assum- 

 ing this to be the liver of a small carnivorous animal or of a rodent. 

 This brings us to the end of our facts concerning the main portion of 

 our section. Deduction will carrv us no further, I think. 



But there was another part of our slide which, under the low power, 

 seemed a mass of black dots, and which has a different color from the 

 remainder of the tissue. What of this ? Let us apply the same methods 

 of investigation to this as to the rest of the section and from the facts 

 observed reach our conclusions. 



