18 



Necessity for the existence of TENDONS .Their nature, struc- 

 ture, uses, and singular arrangement Further remarks on 

 the voluntary and involuntary muscles. 



LECTURE X. 



The Circulation. 



Recapitulation Further remarks on the transmutation of or- 

 gans. 



Necessity of a circulatory apparatus What is a BLOOD VESSEL? 

 Analogy to alimentary canal Cerous coat the only es- 

 sential one Vessels of bone Cellular coat Muscular or 

 fibrous coat Vessels conveying the blood from the organs 

 VEINS Vessels conveying the blood to the organs 

 ARTERIES Vessels essentially composed of cellular tissue 

 The architects of their own structure. 



Blood-vessels Their tonicity Philosophy of faintingStruc- 

 ture of an artery Tree-like form of the VASCULAR SYSTEMS 

 Direction of the current in the arteries and veins Uni- 

 versal penetration of blood-vessels Distribution No 

 vessels proper to cellular-tissue Vessels pass to every 

 fibre of muscles Few vessels in cartilage, ligament, tendon, 

 and other parts approaching cellular-tissue in organisation 

 Their vessels seldom admit red blood Vessels nume- 

 rous in bone Vessels of vessels, to supply fibrous or mus- 

 cular coat, &c. 



Necessity for common centres of the circulation Centres some- 

 times resemble large blood-vessels In other cases, they 

 are -concentrated into the form of hollow muscles, or 

 HEARTS Animals have two, three or more hearts Man 

 has four The centres and the arteries are the motors of 

 the circulation. 



Forms of CIRCULATORY APPARATUS In perfect insects In 

 larvae In worms Circulation in the earth-worm. 



Of arterial hearts, and venous hearts Heart of the tadpole 

 Use and structure of hearts. 



Universal serous lining of the whole vascular system The 

 cavities of the blood-vessels have no direct communication 



