14 



Anatomy of the Rabbit. 



Fig. 7. Hyaline cartilage: 

 cell; 1., lacuna; m., matrix. 



.1. 



cartilage 



cells, chromatophores, and partly to the presence of pigment granules in 

 epithelium. The absence of pigmentation in animals belonging to species 

 normally colored — albinism — is indicated by the white coloration of the 

 hair and by the pink coloration of the eyes, the latter being due to the 

 circumstance that the bloodvessels of the vascular tunic are not concealed 

 by pigment. 



B. Skeletal Tissues. 



The skeletal tissues are solid forms of connective tissue which, on 

 account of their more permanent shape, are better adapted to form a 

 "> support for the body. They are 



pr~ ----- — -^g^—--- .. ; ,~i — m. of two kinds — cartilage and bone. 



Simple or hyaline cartilage 

 (Fig. 7) is a semi-solid and some- 

 what resilient material of a bluish 

 or pearly coloration. It consists of 

 a homogeneous matrix in which 

 the cells are imbedded. The cells 

 are distributed singly, or more 

 often in groups of two to four, 

 each group being contained in a 

 small oval space, the cartilage 

 lacuna. The size of the spaces, and also their distance apart, is subject 

 to great variation. The addition of fibrous elements, usually of white 

 fibres, produces a modification known as fibrocartilage. White fibro- 

 cartilage occurs in certain situations, as in the symphysis of the pelvis, 

 or in connection with the interarticular menisci and at the capsular 

 margins of the joints. 



In the adult skeleton cartilage is 

 present only in small amount. It 

 forms the articular surfaces of 

 joints, the ventral portions or 

 costal cartilages of the ribs, and a 

 portion of the nasal septum ; it is 

 also found uniting the basal bones 

 of the skull. In the embryo, how- 

 ever, it forms the entire skeleton, 

 with the exception of a small por- 

 tion which, as described below, is 

 formed of membrane bone. In the 

 course of development, except in 

 the situations indicated, the carti- 

 lage is replaced by bone. 



Bone is a compact, resistant, but yet somewhat elastic tissue, possess- 

 ing much greater strength than cartilage, and therefore forming a more 

 perfect skeletal support. As indicated below, its appearance as a tissue 

 differs somewhat according to its mode of formation. The more typical 

 structure (intramembranous bone) is illustrated in the accompanying 

 figure (8) of a ground transverse section of the dried shaft of the femur. 



Fig. 8. Intramembranous bone; from a 

 ground section of the rabbhVs femur: c.l., 

 circumferential lamellae; h.c, Haversian 

 canal; h.l., Haversian lamellae; i.l., inter- 

 stitial lamellae; lac., lacuna. 



