18 BOVINE PATHOLOGY. 



interference with function when sucli displacement also 

 causes change of structure. Thus, most of the non-malig- 

 nant tumours are said to consist of normal tissue-elements 

 out of place, and may exist without seriously disturbing vital 

 functions until their bulk causes them to interfere with 

 neighbouring parts in a purely mechanical manner; and as 

 soon as structural changes of these neighbouring parts 

 causes them to become secondarily involved, the disease as- 

 sumes a more urgent character. Again, a displaced bowel in 

 a case of hernia causes no inconvenience nor true patholo- 

 gical condition until it becomes strangulated, and thus 

 structurally disordered. Displacement simply of tissues 

 seldom occurs. Changes in size of a tissue-element may 

 be of increase or decrease, and these may be due to altera- 

 tion of constituents, or to simple variations in their quan- 

 tity. The various degenerations are changes in consti- 

 tuents generally either of a retrograde or a retrospective 

 character. To understand this, we must recall to our 

 minds the elementary structure of the body. It originates 

 as a simple cell, or even earlier, perhaps, a simple mass of 

 protoplasm. This cell is endowed with all the properties of 

 a living organism, dependent upon the high vitality of its 

 protoplasm ; hence it exhibits the phenomena of irritability, 

 contractility, spontaneous power of movement, and repro- 

 ductive energy. All the elements of the adult body are 

 lineal descendents of this primitive element, but each has 

 progressed in a special line; hence, in a muscle-cell con- 

 tractility is the prominent property ; in a nerve-cell spon- 

 taniety or irritability, and in white fibrous tissue-corpuscles 

 probably the control of local nutrition. Under certain 

 diseased conditions, each of these forms of cell is liable to 

 regain some of its lost or dormant powers; thus, the 

 tissue-corpuscle becomes a reproductive cell, and proli- 

 ferates freely in suppuration ; the muscle-cell exhibits 

 spontaneity. Such are retrospective degenerations. Re- 

 trograde metamorphoses are much more frequent, the 

 principal being mucoid, colloid, and fatty degenerations. 



Mucoid Degeneration consists in such an alteration of 

 the tissues that they assume a mucus-like character. It 



