62 PROXIMATE PRINCIPLES IN GENERAL. 



up of minute bodies, of definite size and figure, which are so small 

 as to be invisible to the naked eye, and which, after separation 

 from each other, cannot be further subdivided without destroying 

 their organization. They are, therefore, called "anatomical ele- 

 ments." Thus, in the liver, they are hepatic cells, capillary blood- 

 vessels, the fibres of Glisson's capsule, and the ultimate filaments 

 of the hepatic nerves. Lastly, two or more kinds of anatomical 

 elements, interwoven with each other in a particular manner, form 

 a "tissue." Adipose vesicles, with capillaries and nerve tubes, 

 form adipose tissue. White fibres and elastic fibres, with capillaries 

 and nerve tubes, form areolar tissue. Thus the solid parts of the 

 entire body are made up of anatomical elements, tissues, organs, 

 systems, and apparatuses. Every organized frame, and even every 

 apparatus, every organ, and every tissue, is made up of different 

 parts, variously interwoven and connected with each other, and it 

 is this character which constitutes its organization. 



But beside the above solid forms, there are also certain fluids, 

 which are constantly present in various parts of the body, and which, 

 from their peculiar constitution, are termed " animal fluids." These 

 fluids are just as much an essential part of the body as the solids. 

 The blood and the lymph, for example, the pericardial and synovial 

 fluids, the saliva, which always exists more or less abundantly in 

 the ducts of the parotid gland, the bile in the biliary ducts and the 

 gall-bladder : all these go to make up the entire body, and are quite 

 as necessary to its structure as the muscles or the nerves. Now, if 

 these fluids be examined, they are found to be made up of many 

 different substances, which are mingled together in certain propor- 

 tions; these proportions being constantly maintained at or about 

 the same standard by the natural processes of nutrition. Such a 

 fluid is termed an organizing fluid. It is organized by virtue of the 

 numerous ingredients which enter into its composition, and the 

 regular proportions in which these ingredients are maintained. 

 Thus in the plasma of the blood, we have albumen, fibrin, water, 

 chlorides, carbonates, phosphates, &c. In the urine, we find water, 

 urea, urate of soda, creatine, creatinine, coloring matter, salts, &c. 

 These substances, which are mingled together so as to make up, in 

 each instance, by their intimate union, a homogeneous liquid, are 

 called the PROXIMATE PRINCIPLES of the animal fluid. 



In the solids, furthermore, even in those parts which are appa- 

 rently homogeneous, there is the same mixture of different ingre- 

 dients. In the hard substance of bone, for example, there is, first 



