TISSUES, ORGANS, AND SYSTEMS. 53 



1. The external cutaneous .system, consisting of the corium, 

 the epidermis, the horny tissues, and the larger (lacteal gland 

 and smaller glands of the skin. 



2. The osseous system, consisting of the bones, cartilages, 

 ligaments, and articular capsules. 



3. The muscular system, consisting of the muscles of the 

 trunk and of the extremities, the tendons, fasciae, tendinous 

 ligaments, and bursa mucosae. 



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

 central organs, the nerves and the higher orgaus of sense. 



5. The 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 respiratiou, with the thymus and thyroid, the 

 salivary glands, the liver, and the spleen. 



7. The urinary and sexual systems. 



As the separate organs and systems are particularly con- 

 sidered 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 generalities concerning the 

 organs. . 



§ 21. 



Epidermic Tissue. — The morphological character of the 

 epidermis 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 sub- 

 stance, in part also mucous ; and at first all possess easily soluble 

 protein membranes, which however, subsequently, become 

 partially changed into a substance which more or less resists 

 acids and alkalies, — the so-called horn. The physiological im- 

 port of the epidermic tissue is to serve as a defensive covering 

 to those parts of the organism which abound in vessels and 

 nerves, and by the activity of its elements to take part in 

 secretion and absorption. All epidermic tissues are non-vas- 

 cular, and support themselves from a plasma which is yielded 



