477 



(3) Jfiisdes.— In these the cells lie end to eud, forming long fibers 

 which have the power of contraction, and the connective tissue is in 

 small quantity, serving the passive purpose of a band around the 

 contractile elements. 



(4) In cartilacje a mass of firm amorphous substance, with no vas- 

 cularity and little vitality, forms the bed for the chondroplasts or 

 cells of this tissue. 



(5) Bone differs from the above in having the amorphous matter 

 impregnated with lime salts, which gives it its rigidity and firmness. 



(6) Epithelia and endotheUa, or the membranes which cover the 

 body and line all of its cavities and glands, are made up of single 

 or stratified and multiple layers of cells bound together by a glue^'of 

 amorphous substance, and resting on a layer composed of m^ore or 

 less fibers. AVlien the membrane serves for secreting or excreting 

 purposes, as in the salivary glands or the kidneys, it is usually sin> 

 pie when it serves the mechanical purpose of protecting a part, as 

 over the tongue or skin it is invariably multiple and stratified, the 

 surface wearing away while new cells replace it from beneath. 



(7) In nerves, stellate cells are connected by their rays to each 

 other, or to fibers which conduct the nerve impressions, or they act 

 as receptacles and storehouses for them, just as the switch board of 

 a telephone system serves to connect the various Avires. 



All of these tissues are supplied with blood in greater or less ouan- 

 tity. The vascularity depends upon the function which the tissue is 

 called upon to perform. If this is great, as in the tongue, the luno-s 

 or the sensitive part of the foot, a large amount of blood is require'd' 

 if the labor is a passive one, as in cartilage, the membrane over the 

 withers, or the tendons of the legs, the vessels only reach the periph- 

 ery, and nutrition is furnished by imbibition of the fluids brought to 

 their surface by the blood vessels. 



Blood is brought to the tissues by arterioles, or the small termina- 

 tions of the arteries, and is carried off from them by the veinlets or 

 the commencement of the veins. Between these two systems are 

 small delicate networks of vessels called capillaries, which subdivide 

 into a veritable lace-work so as to reach the neighborhood of everv 

 element. ^ 



In health the blood passes through these capillaries with a reo-ular 

 current, the red cells or corpuscles floating rapidly in the fluid in the 

 center of the channel, while the white or amoeboid cells are attracted 

 to the walls of the vessels and move very slowly. The supplv of blood 

 IS regulated by the condition of repose or activity of the tfssue and 

 under normal conditions the outflow compensates exactly the supply 

 The caliber of the blood vessels, and consequently the amount of 

 blood which they carry, is governed by nerves of the sympathetic 

 system m a healthy body with unerring regularity, but in a diseased 

 organ the flow may cease or be greatly augmented. In health a tissue 



