Tenderness in Cattle. S9 



liberating heat, and other matters, in the tissues, producing 

 carbonic acid ; which, with other material discharged from 

 the tissues, principally from muscular parts, is poisonous 

 in a high degree. Such excretory matters pass outward to 

 the lungs, and to some extent to the skin, but mainly to 

 the lungs, whence they are exhaled as poisonous excretions. 

 During this process of change and nutrition, the most heat 

 passes into the circulation from parts where the most re- 

 newal or change in the tissue takes place ; considerable 

 blood heat being derived from changes taking place in the 

 liver. In considering the sources of tenderness in- cattle, 

 M'e are, however, chiefly concerned about the sources that 

 supply heat in the muscles and the skin. And it is espe- 

 cially important to remember that the heat that supplies 

 sensible warmth in any part or organ is according to ac- 

 tivity in the part. Thus heat is made active and sensible 

 in the muscles of locomotion, according to activity ; and 

 this is true of all parts of the body, incltiding the skin. 



The sensation of cold affects the skin more than other 

 parts, because the surface is supplied with many nerves, 

 and exposed to loss of heat by evaporation, or the escape 

 of heat into the cooler surrounding air, on the principle 

 of equalization of temperature. 



The extent of assimilation during which heat is liberated 

 and becomes sensible as warmth, so increasing the tempera- 

 ture of the blood and skin, is according to two condi- 

 tions, namely : The activity of cattle, and their corre- 

 sponding activity of breathing in the first place ; and 

 secondly, to the extent of the tissue, or bulk and weight 

 of the organ in which heat is made active, so increasing its 

 warmth. The quantity of heat liberated is according to 

 the extent of flesh or skin substance in which this process 

 occurs during assimilation. Thus there is more heat liber- 

 ated in a thick skin than in a hide of medium thickness, 

 1 



