156 



ANATOMY AND PHYSIOLOGY OF 



the heart are composed of elastic cartilage, 

 which enables them to work with ease. In 

 some diseases, however, they become ossi- 

 fied. This, of course, is fatal. The heart 

 and its appendages are also subject to other 

 diseases, called dilatation, softening, hard- 

 ening, etc. Now, the blood, having been 

 brought from all parts of the system by the 

 veins, enters into the vena cava ascending 

 and descending portion, which empty them- 

 selves into the right auricle ; and this, 

 when distended with blood, contracts, and 

 forces its contents into the right ventricle, 

 which, contracting in its turn, propels the 

 blood into the pulmonary arteries, whose 



numerous ramifications bring it in con- 

 tact with the air-cells of the lungs. It 

 then assumes a crimson color, and is then 

 adapted to build up and supply the waste. 

 Having passed through the vessels of the 

 lungs, it continues on, and passes into 

 the left auricle: this also contracts, and 

 forces the blood through a valve into the 

 left ventricle. This ventricle then con- 

 tracts in its turn, and the blood passes 

 through another valve into the great aorta, 

 from which it is distributed into the whole 

 arterial structure : after going the rounds of 

 the circulation, it is again returned to the 

 heart by the veins. 



EXAMINATIOXS OX THE NATURE AND PROPERTIES OF BLOOD. 



Q. What are the properties of blood ? — A. In 

 health, it is a smooth homogenous jBuid, of unctuous 

 adhesive consistence, of a slightlj' saline taste, and of a 

 specific gravity somewhat exceeding that of water. It 

 exhales a vapor which has a peculiar odor ; this, how- 

 ever, differs in various animals. 



Q. Does the blood always preserve the same den- 

 sity ? * — A. No. Its density is liable to great variations, 

 under the states of rest, labor, disease, and health. 



Q. What do you understand by the " crassamentum" 

 of the blood? — A. It is supposed to consist chiefly 

 of fibrin. 



Q. How is it colored ? — A. It owes its peculiar color 

 to what is termed the red globules, which are entangled 

 in it during its coagulation. 



Q. How can tliis be demonstrated? — A. By long 

 continued ablution in water, the red particles are Uber- 

 ated ; and we have remaining a wliite, sohd, and elas- 

 tic substance, which has all the properties of fibrine, 

 and is almost exactly similar to the basis of muscle. 



Q. By what name was fibrine formerly known ? — A. 

 Coagulable lymph. 



Q. What is the form of the red globules of the 

 blood? — A. The Abbe de la Torre, who examined 

 them under mici'oscopes of considerable power, states 

 that they obtained the appearance of flattened aimular 

 bodies, with a depression, sometimes perforation, in the 



*Dr. B. Babington is of opinion tliat the blood, whilst circulating 

 in the vessels, consists of two parts only — a fluid which he calls liquor 

 iaiig'i/inf.';, and red globules; and he is induced to belieye, from his 

 experiments, that fibrin and serum do not exist as such in the circu- 

 lating fluid, but that the liquor sanguinis, when removed from the 

 vessels, and no longer subjected to the laws of life, has then, and not 

 before, the property of separating into fibrin and serum. Med. Chi- 

 rvrg. Transact, vol. xvi. pt. 2. Lond. 1831, and art. Blood (morbid 

 conditions of the), in Cyclop, of Anat. and Physiol. Lond. 1836. 



centre, but they differ in size and shape in various 

 animals. 



Q. By what means is the blood colored? — A. By 

 means of iron and oxygen. 



Q. Describe the properties of the serum ? — A. It is 

 the yellow fluid part that is left after the separation of 

 the crassamentum ; it is of a saline taste, and homoge- 

 nous, adhesive consistence. 



Q. What effect has a temperature of 160° on it? — 

 A. The whole is converted into a firm white mass, per- 

 fectly analagous to the Avliite of an egg wliich has been 

 hardened by boiling. 



Q. Can any Hquor be extracted from the serum after 

 having been coagulated by heat? — A. Yes. If the 

 coagulum be cut into slices, and subjected to gentle 

 pressure, an opaque liquor di-ains from it, which is called 

 the serosity. 



PERICAEDIUM. 



Q. By what is the heart surrounded? — A. The 

 pericardium. 



Q. AVhat is the structure of this? — A. It is a fibro- 

 serous membranous bag, composed of two coats ; one 

 fibrous, the other serous ; these are miited by cellular 

 tissue. 



Q. AVhat are its connections? — A. It is attached to 

 the sternum, pleura, diaphragm, and to the roots of 

 the large blood-vessels at the base of the heart. 



Q. What is the function of the serous surface of the 

 pericardium? — A. To secrete the liquor pericardii. 



Q. What is the use of this Uquor ? — A. It serves to 

 protect its own sm-face, and that of the heart, from 

 friction. 



Q. What oflice does the pericardium perform? — A. 

 It sustains the heart in its proper situation. 



