tion. It is characterized by a rich vascular .supply. Each 

 lobule contains a closed blood vascular system. An artery 

 enters each lobule, and breaks up into a thick capillary network. 

 which gives origin usually to two veins. This is the first we 

 have seen of the so-called blood vascular units, of which much 

 will be said later on. The fat, as will be observed, is made up 

 of many lobules, which, as far as the blood-supply is concerned, 

 are all units in themselves. 



For many interesting points in connection with fatty degen- 

 eration in cells, and the relation of fat production to food, the 

 reader is referred to works on pathology and physiology. 



2. Cartilage. 



Cartilage is distinguished from the connective tissues by the 

 hard consistency of its ground substance and the characteristic 

 appearance of the cells. It forms a transition between con- 

 nective tissue and bone. 



On boiling, cartilage gives chondrin, which is not identical 

 with glutin. For the properties and chemical composition of 

 this the reader is referred to works on physiological chemistry. 



The surface of cartilage is, with the exception of places where 

 it lies directly on the bone or forms articular surfaces, covered 

 by a sheath of fibrillar connective tissue, the perichondrium. 

 This contains the blood-vessels, and thus plays an important 

 part in the nourishment, the growth, and new formation of 

 cartilage. According to the different character of the inter- 

 cellular substance, we distinguish three kinds of cartilages : 



(a) Hyaline cartilage ; 



(b) Elastic cartilage ; 



(c) Fibrous cartilage. 



The cells of these three kinds of cartilage are in general simi- 

 lar. We shall therefore describe the cells of hyaline cartilage 

 only. 



(a) Hyaline Cartilage. The cells are round or oval, and 

 often arranged in groups (Fig. 36). When they lie near one 

 another they are pressed together, so that adjacent sides are 

 flattened. The protoplasm is finely granular, and contains in 



