22 BOVINE PATHOLOGY. 



thus the bladder may have its walls thickened when any 

 obstruction in the urethra interferes with the passage of 

 urine. The reverse of this is Atrophy or wasting, which 

 is described as of two kinds, simple and numerical. The 

 former depends upon decrease in size of the proper 

 elements of a tissue dependent upon deficient supply of 

 nutritive matter, the latter is a more advanced stage of 

 the same state in which actual removal of tissue elements 

 has occurred. Atrophy may result from an imperfect 

 supply of blood or from imperfect ability to appropriate 

 nutritive matter, such as often results from inflammation. It 

 may be difficult to ascertain this state from simple inspec- 

 tions of organs, for as the useful elements are removed the 

 connective elements may be increased in quantity, or dis- 

 placement of some material into the organ may serve to 

 maintain its size. The additions op material to an organ 

 in almost all cases take place from the blood, and hence 

 have the character of infiltrations. They may be solid, 

 liquid, or gaseous. Liquid matters most frequently over- 

 flow from the blood, or are removed in excess from that 

 fluid by over-excited tissue elements. They contain solid 

 matters in solution, and as their fluid portions are most 

 readily removed by absorption, solid deposits may remain 

 behind. These latter either become organised by exten- 

 sion of vessels into them, undergo calcareous change 

 and become permanent (but in the condition of foreign 

 matters), or undergo retrograde changes, especially the 

 fatty, and become absorbed. We shall have more to 

 say about these processes when treating on inflammation. 

 Accumulation of liquid added material constitutes Dropsy. 

 Gas sometimes occurs in a tissue either as a result of 

 gangrenous change of the tissues (the blood for instance) 

 as in black quarter, or as a result of ill-explained nutri- 

 tive changes in a part, or entry of air through an external 

 or pulmonary wound. The gases which occur are such as 

 normally exist in the blood or the atmosphere. Having 

 dealt with the general changes which structures undergo 

 as a result of diseased processes, we must next examine 

 the characters of those processes themselves. 



