PHYSIOLOGICAL 115 



, a racial or at any rate an individual characteristic. Apart from 

 the degree of development of connective tissue, ''toughness" 

 and "tenderness" in meat are due largely, as is well known, to 

 the denseness of the muscle fibres and the thickness of their 

 cell walls, characteristics which are developed by use, that is, 

 by muscular exercise. 



The muscular development necessary for remunerative beef- 

 production must depend further upon the shape of the skeletal 

 framework, that is to say, it is an anatomical characteristic of 

 particular breeds (see Chap. X). Moreover, beef and milk- 

 production may be usefully combined in the same breed or 

 strain, and of this fact the living proof exists in the "dual- 

 purpose" Shorthorn and Lincoln Red cattle, and to a less 

 extent in certain other breeds. But to what degree a good beef 

 carcase can be united in the same race with a deep-milking 

 propensity is still an open question. It cannot be definitely said 

 that the two characteristics are physiologically incompatible, 

 though it is probably quite correct that for reasons of nutrition 

 they cannot easily co-exist in the same individual. On the 

 alternation between the growth of dermal fat and the secretion 

 of milk we find Sheldon writing as follows : " On animals that are 

 well adapted for both milk and beef, there will always be soft, 

 velvety skin, which will feel mellow to the touch as if it rested 

 on a second underskin like a cushion. This 'underskin' con- 

 sists of a network of cells, called 'cellular tissue,' and when a 

 cow is not in milk fat soon accumulates in it, and forms the 

 ' quality ' or ' handling ' which indicates the extent to which she 

 may be considered fit for the butcher. If the cow is in milk 

 this fatty accumulation in the cellular tissue goes instead to 

 form cream in the milk 1 ." These statements are crudely and 

 inaccurately expressed, since there are reasons for believing 

 that the fat contained in milk is manufactured in the cells of 

 the mammary gland, and not carried thence from elsewhere, 

 but nevertheless the general contention implied (namely, that 

 the increased nutriment required for an organ in a state of 

 functional activity involves a depletion of tissue elsewhere) is 

 not without a solid substratum of truth. 



1 Sheldon, Dairy Farming, London. 



82 



