ANIMAL HEAT. 573 



any individual organ, by which disease in one becomes a cause of disorder in 

 the rest, is, however, to be very differently explained. We have examples 

 of this in Inflammatory affections of the Mucous membranes, which usually 

 extend themselves to the remaining constituents of the organs of which they 

 form a part ; and in those of the Serous membranes, which almost always 

 follow inflammation of the organs they invest. Here the local disturbance of 

 one part appears sufficient to account for the extension of it to another that is 

 closely connected with it by vessels and nerves ; this has been termed the 

 Sympathy of Contiguity. The Fibrous membranes are less liable to be affected 

 in this manner than are most other tissues ; and the reason appears simply 

 this, that there is usually less vascular connection between them and the 

 adjacent parts than there is in the case of the Serous membranes. Hence the 

 Fibrous membranes frequently act as insulators, preventing the spread of dis- 

 ease to adjacent parts. 



718. The general characters of the processes of Nutrition and Secretion are 

 so nearly allied, that what has been stated of the Pathological states of the 

 former, is nearly as applicable to those of the latter. Although it is unquestion- 

 able that disordered Secretion may result from a purely local cause, acting on the 

 solid tissue of the part affected, yet there is also increasing reason to believe, that 

 in a large number of cases, the abnormal character of the product is in reality 

 a result of the abnormal state of the Blood from which it is separated ; and 

 that the organ itself is still performing a healthy function, in separating from 

 the blood that which would be injurious to it. This leads us to refer such 

 disorders to causes much more remote than those which were formerly sup- 

 posed to operate ; but they are undoubtedly nearer the true ones. Such a 

 view has been prosecuted by Dr. Prout in regard to the abnormal conditions 

 of the Urine, with great success ; and there can be little doubt that it is also 

 applicable to the Biliary secretion, on the true chemical nature of which there is 

 scarcely yet an agreement among Chemists, and whose pathological conditions, 

 therefore, are, and must long remain, comparatively obscure. It is obvious 

 that, if the Assimilation of Nutritive matter be in any respect wrongly per- 

 formed, the products of the Decomposition of the Tissues (in which these 

 secretions probably originate, 648) must also be different ; and our remedial 

 measures must often be directed, therefore, not so much to the Secreting organ, 

 as towards the previous operations. These hints, which may to some appear 

 of too abstract a character to be of any practical value, are introduced here for 

 the purpose of directing the intelligent Student in the path that will conduct 

 him to fields of inquiry scarcely yet trodden, and fertile in the most valuable 

 results. In the present unsettled state of opinion upon many of the highest 

 questions in Pathology, it would be absurd to attempt to lay down, in a dog- 

 matic form, what is; but much may be done, by purifying the science of what 

 is not ; and here a sound Physiology affords most valuable assistance.* 



II. Animal Heat. 



719. All the vital actions that have been considered in the preceding pages 

 require a certain amount of Heat, as a condition of their performance ; and in 

 the more elevated tribes of animals, in which (for the very purposes of their 

 creation) a high degree of constancy and regularity is required in these actions, 

 there is a provision within themselves for the maintenance of their tempera- 

 ture at a certain standard. We shall inquire in the first place into the amount 

 of Heat thus generated by Man ; and then into the sources of its production. 



* The Author would particularly refer to Dr. Williams's Principles of Medicine, as 

 giving the best general view of this subject that has yet been published, in this country 

 at least. 



