Page:The American Cyclopædia (1879) Volume I.djvu/493

ANATOMY 461 minute anatomy. Surgical anatomy treats of the relations of organs to each other, in each region of the body, such as the positions, forms, dimensions, structure, and peculiarities of nerves and vessels, muscles, glands, and mem- branes, in the head, the trunk, and the limbs, a proper knowledge of which is necessary to guide the surgeon in , his delicate and difficult operations. He must know where to cut and what to avoid in operating on the living body ; for the life of the patient might be jeoparded if the surgeon were not well acquainted with the relative anatomy of vital organs. Descrip- tive anatomy treats of the distinct systems which pervade the whole frame, or perform a certain class of functions in the organism ; such as the bones of the skeleton, the muscles, the skin, and the nerves of the whole body ; the digestive system ; the blood vessels ; the respiratory organs ; the generative and the uri- nary apparatus ; the blood and the secretions. General anatomy treats of the different tissues which compose the special organs or classes of organs in different parts of the body ; such as the three distinct coats of the stomach, *'. <?., the mucous membrane, the muscular coat, and the serous membrane or peritoneal covering ; the areolar or connective tissue, found between the mucous and muscular layers, and disseminated more or less extensively throughout the body. Minute anatomy investigates the elementary basis of organic nature, and by the aid of chem- istry and the microscope observes and analyzes the atomic and cell structure of the tissues which compose the organs of the body; the fluids and contents are also subjected to this minute analysis. Animal anatomy was scantily and almost exclusively studied by the ancients ; human anatomy was fairly commenced by the Italian schools of the 14th, 15th, and 16th cen- turies ; the descriptive branch was chiefly cul- tivated throughout Europe until the end of the 18th, when Bichat instituted and almost origi- nated the systematic study of general anato- my. Microscopic observations had been made by Malpighi and other anatomists, but many of the great discoveries of comparative and general anatomy have been made in the pres- ent age ; and the systematic study and de- velopment of minute anatomy date from the improved construction of the compound micro- scope in 1$32, before which time it was impos- sible to make much progress in this most im- portant branch of science. Descriptive or special anatomy is limited to the study of the parts which form the body of one type or indi- vidual, or of the two sexes of one species, as man and woman. It does not, however, ex- clude reference to age and difference of race. The organs of the body have been classed in various ways by different anatomists, and most- ly according to the nature of their special structure and peculiarity of use or function. Bichat's method, slightly modified, is most in use, and is perhaps the best. By this the or- gans are classed as follows : I. Organs pertain- ing to the animal, voluntary, or relational func- tions. II. Organs pertaining to the nutritive functions. III. Organs pertaining to genera- tion, or the reproductive functions. To the first class belong the organs of locomotion, in- nervation, voice, and sensation. 1st. The skele- ton, composed of bones, cartilages, ligaments, and joints, as instruments of locomotion and forming the subject of what is termed oste- ology. 2d. The muscular system, composed of muscles, tendons, sheaths, and their append- ages, as agents of locomotion, forming the sub- ject of myology. 3d. The nervous system, composed of medullary white substance and gray vesicular matter, enclosed in sheaths of serous and fibrous membrane, forming the brain, spinal cord, ganglia, and nerves. The special study of the structure and functions of the nervous system and appendages is termed neurology. 4th. The vocal organs, as an appa- ratus of relational use between man and the external world, are the larynx or throat, and the mouth ; the one as an organ of the voice, and the other as an organ of articulation or speech. 5th. The special organs of sense are distinguished into proper and common ; taste, smell, sight, and hearing belong to the former, and touch, the sense of temperature, and the muscular sense of resistance, weight, lassitude, &c., belong to the latter. The mouth, the nose, the eyes, and the ears are special organs, but the whole external surface of the body serves for the sense of touch and temperature, while the whole internal muscular structure seems to be affected by the sense of lassitude, and the muscular parts of the trunk and limbs are affected by the sense of resistance to external weight or force. To the second class of organs, pertaining to the functions of nutrition, belong the organs of digestion, respiration, circulation, secretion, and excretion. 1st. The digestive system consists of the alimentary canal, to- gether with its accessory organs, such as the salivary glands, the liver, and the pancreas. The alimentary canal, consisting of its succes- sive portions, namely, the mouth, oesophagus, stomach, small intestine, and large intestine, receives the food and accomplishes its digestion by the mechanical operation of the teeth in mastication, followed by the modifying action of the various digestive secretions. 2d. The heart is the centre of the circulatory system, which consists of two distinct circuits, called pulmonary and systemic. From the right ventricle of the heart the dark impure blood is sent through the pulmonary arteries into, the lungs, where the minute capillary blood vessels are exposed to the almost direct con- tact of the air, from which oxygen is absorbed to vivify the blood, giving it a bright scarlet red. A thin membrane intervenes between the air in the lungs and the blood, but this does not impede the absorption of oxygen and the exhalation of carbonic acid gas, the one to give new life and the other to rid the blood of poisonous gas and effete matter. When thus