74 GENERAL ANATOMY OF THE TISSUES. 



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 intestinaUs, 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 : — 



1. The external cutaneous syste7n, consisting of the corium, the epi- 

 dermis, the horny tissues, and the larger (lacteal gland) and smaller 

 glands of the skin. 



2. TJic osseous system, consisting of the bones, cartilages, ligaments, 

 and articular capsules. 



3. TJte muscular system, consisting of the muscles of the trunk and 

 of the extremities, the tendons, fascioe, tendinous ligaments, and hursce 

 mucosce. 



4. The nervous system, composed of the larger and smaller central 

 organs, the nerves and the higher organs of sense. 



5. Tlie vascular system, consisting of the heart, the blood and lymph- 

 vessels, and the lymphatic glands. 



6. The intestinal system, composed of the intestinal canal, the organs 

 of respiration, with the thymus and thyroid, the salivary glands, the 

 liver, and the spleen. 



7. The urinal and sexual systems. 



As the separate organs and systems are particularly considered in the 

 special part of this work, it is not necessary to speak at greater length 

 of them here, and it is only requisite to define the tissues somewhat 

 more closely — taking occasion at the same time to refer to some gene- 

 ralities concerninfj the organs. 



§21. Epidermic Tissue. — The morphological character of the epi- 

 dermis is, that it is wholly constituted by independent cells intimately 

 united together without any visible matrix, which are generally nucleated 

 and in part are true vesicles, while in part they are metamorphosed into 

 solid scales. In its chemical characters this tissue is but little known, 

 though this much has been made out, that its cells contain chiefly an 

 albuminous substance, in part also mucous ; and at first all possess easily 

 soluble protein membranes, which however, subsequently, become par- 

 tially changed into a substance which more or less resists acids and 

 alkalies, — the so-called horn. The physiological import of the epidermic 

 tissue is to serve as a defensive covering to those parts of the organism 



