OF NON- VASCULAR ANIMAL TISSUES. 177 



Structure. They, like the fibro-cartilages of symphyses, consist of an external fibrous 

 and of a central cartilaginous portion. At the early periods of their development, the 

 cartilaginous is more abundant than the fibrous portion, and it is almost entirely 

 composed of corpuscles. As age advances, the fibrous portion increases in quantity ; 

 and towards the later periods of life, the corpuscles of the cartilaginous division are 

 mixed with fibrous tissue. 



Of the Vessels of F'lhro- Cartilage. 



Respecting the vascularity of the fibro-cartilages, Bichat says, " Pen de sang p^ 

 n^tre leur syst^me vasculaire dans I'^tat ordinaire, mais dans I'inflammation ils sont 

 extr^mement inject^s*." 



Professor Todd says, " They (the fibro-cartilages) are more vascular than pure car- 

 tilage, but in the natural state they admit very few vessels carrying red blood -(•." 



MuLLER, as quoted above, says "they have blood-vessels, although in a small 

 number." 



Of the Vessels of Fibro- Cartilages of the First Class. — 1. Of the inter-vertebral 

 substances. — I have made numerous injections of the intervertebral substance in Man 

 and animals of various ages, and have found that the external more fibrous portion 

 is pierced by arteries of considerable size ; these are guarded from compression by 

 the dense nature of the fibrous tissue through which they pass. They course towards 

 the central cartilaginous portion, into which, however, they do not penetrate, but in 

 its confines they form large convoluted dilatations, from which the recurrent vein 

 arises. The extreme edge of these vascular convolutions presents a line which may 

 be considered as the boundary between the fibrous and cartilaginous portions of the 

 intervertebral fibro-cartiiage. See Plate XV. fig. 6. 



2. The following is the result of a careful examination of the vessels of the sacro- 

 iliac Jibro-cartilage in the human subject, at various periods of its development. 



a. In the fifth month of foetal existence the vessels of the sacro-iliac fibro-cartilage 

 form a conglomerated mass of large and tortuous arteries and veins contained in the 

 external part of the fibrous portion. Here and there a few more delicate branches 

 diverge from this mass to a slight distance towards the central cartilaginous portion, 

 at the border of which they terminate in dilated extremities. 



b. In the foetus o^six months the convoluted arteries are prolonged to the circum- 

 ference of the cartilage, where they divide and subdivide, each branch terminating in 

 a dilatation, which frequently communicates with the one adjacent to it, and from 

 this dilatation or series of dilatations the recurrent veins arise. 



c. In the foetus of nine months these vessels are considerably increased in length ; 

 they are more distant from each other, and their extremities no longer present the 

 large dilatations. 



* Anatomie G^ndrale. Article, Organization du Systhne Fibro-Cartilagineux. 

 t Cyclopaedia of Anatomy and Physiology. Article, Fibro- Cartilage. 



