CHAP. I.] DIFFERENT PARTS OF THE BODY. 3 



intestines, etc. The pelvic cavity contains the bladder, rectum, 

 and generative organs. Connected with the upper part of the 

 ventral cavity are two small cavities, the buccal cavity, or mouth, 

 containing the tongue, teeth, salivary glands, etc., and the nasal 

 cavity, containing the organ of smell. 



Different parts of the body. In speaking of the different parts 

 of the body, we usually call each part an organ, and we may say 

 that the human body is made up of organs, each organ being 

 adapted to the performance of some special work or function. 

 Thus the lungs are organs specially adapted for performing 

 the function of respiration, the bones are organs adapted for 

 support and locomotion, the kidneys for secreting urine, etc. 



Every part or organ, when separated into minute fragments, 

 is found to consist of certain textures or tissues. When the 

 body is thus separated or dissected, and analyzed by the aid of 

 the microscope, we find that the number of distinct tissues is 

 comparatively small, and some of these again, although at first 

 sight apparently distinct, yet have so much in common in their 

 structure and origin one with another, that the number becomes 

 still further reduced, until we can only distinguish four distinct 

 tissues, viz. : 



The epithelial tissues. The muscular tissues. 



The connective tissues. The nervous tissues. 



Particles met with in the fluids of the body, such as the little bodies or cor- 

 puscles in the blood and lymph, are also reckoned among these elementary 

 tissues. 



Some organs are formed of a combination of several of the 

 above tissues ; others contain only one or two. Thus the 

 muscles are made up almost entirely of muscular tissue with 

 only a small intermixture of connective tissue, blood-vessels, 

 and nerves ; whilst the ligaments or sinews are composed 

 wholly of a variety of connective tissue. 



On the other hand, there are certain organs or parts of the 

 body not in themselves distinguished by the preponderance of 

 any tissue. Such are : 



Blood-vessels. Synovial membranes. 



Lymphatic vessels. Mucous membranes. 



Lymphatic glands and bodies Secreting glands. 



of like structure. Integument or skin. 

 Serous membranes. 



