224 THE CONTENTS OF THE THORAX. 



ardent spirits ; it yields salts by incineration. . Spontaneous 

 coagulation is not so rapid in the horse as in man, in whom 

 it is completed in seven or eight minutes ; whereas it com- 

 monly requires more than twenty hours to set the blood of 

 the horse. 



The fluid basis of the blood is serum : it serves to dilute 

 it, and it forms about four-sevenths of the whole. It is 

 slightly saline, and less putrefactive than the coagulum. 

 It remains fluid in those degrees of heat between 30 and 

 1 60 degrees Fahrenheit : with a less heat it freezes ; in a 

 greater it partially coagulates. It appears chemically com- 

 posed of albumen, gelatin, saline matter, and a considerable 

 quantity of fluid which drains from it, called the serosity. 

 Serum appears not only the fluid base of the blood, but it 

 also dilutes all the secretions : when morbidly increased, 

 it gives rise to dropsy. The blood, therefore, is con- 

 sidered as a compounded fluid made up of these several 

 parts, and which, considered as an aggregate, is the most 

 essential component of an animal. All parts of the body 

 are formed of it ; and all parts of the body can be resolved 

 again into it, by means of the absorbents ; hence we must 

 conclude that there is a very intimate connexion between 

 the solids and the fluids ; whence Mr. Hunter, and many 

 subsequent physiologists, have been led to consider both 

 as governed by the same laws, and as identified with each 

 other in living properties. 



DESCRIPTION OF PLATE VIII. 



THE CONTENTS OF THE THORAX. 



A, the trachea ; B B, the right lung ; C C, the left lung, 

 both lungs being deprived of their mediastinums ; D, the 

 heart ; a, the oesophagus, or gullet ; b, the common carotid 

 artery, dividing into the right and left carotids ; c, the 

 right vertebral artery ; d, the recurrent nerve of the right 

 side ; e, the par vagum and sympathetic nerves of the right 

 side, journeying in company down the neck. The enlarge- 

 ment perceptible upon the nerves, marks the situation of 

 the cervical ganglion on the sympathetic ; ff, the anterior 

 lobes of the right and left lung ; g g, the posterior lobes of 

 the right and left lung ; h, the small extra lobe of the right 



