52 GENERAL ANATOMY OF THE TISSUES. 



intermixed with fine elastic fibres, and sometimes cartilage 

 cells in small quantities, and almost entirely devoid of vessels 

 and nerves. 



Complex organs are : 



(e.) The smooth muscles and muscular membranes ; and — 



(/.) The transversely striated muscles and muscular mem- 

 branes, both of which, besides their contractile elements, are 

 abundantly intermingled with connective tissue, nerves, and 

 blood-vessels. 



(g.) The nerves, ganglia, and higher central organs of the 

 nervous system, contain besides grey and white nervous sub- 

 stance, many blood-vessels, and special fibrous investments. 



(h.) The vessels are composed of connective and elastic 

 tissue, muscles and epithelium in various proportions, and are 

 provided with vessels and nerves, only in their outermost 

 layers. 



(i.) The bones and teeth, which, together with their charac- 

 teristic tissues, have peculiar soft structures, containing many 

 vessels and nerves, and the former medulla also. 



(k.) The blood-vascular glands, composed of a peculiar glan- 

 dular element, in the form of closed follicles of different kinds, 

 and many blood-vessels; with nerves also, and with abundant 

 but generally non-contractile fibrous tissue. 



(/.) The true glands; glandular follicles, vesicles or tubes 

 with many vessels, nerves, and investing fibrous tissue. 



(m.) The vascular membranes, as the skin, the mucous, 

 serous, and proper vascular membranes, which in a matrix 

 composed of connective and elastic tissue, generally contain 

 very numerous blood-vessels and lymphatics, in part also 

 simple glands and nerves, and are invested by special 

 epithelial layers. 



(n.) The separate organs of the tractus intestinalis, as the 

 tongue, the oral cavity, the pharynx, the oesophagus, the 

 stomach, and so forth, into the constitution of which, mucous, 

 muscular and serous membranes, grouped in various ways, 

 enter. 



(o.) The higher organs of sense, into which almost all the 

 tissues and many more simple organs enter. 



Lastly, the organs enter into the formation of peculiar 

 systems, of which we may distinguish the following : 



