ESSAYS 



669 



The increase due to growth, being of the same composition as the lean animal, 

 may be added to the weight of the latter, and the true fattening increase 

 expressed as if growth and fattening had taken place successively, thus : 



To facilitate comparison with the ox, the data in the preceding tables may be 

 summarised as follows : 



The calculations recorded above were based on the assumption that growth 

 includes formation of fat in the proportion in which it is present in the lean 

 animal. This was not the same in all cases ; the ox contained substantially less 

 fat than the others. The meat produced by growth was, therefore, less valuable, 

 weight for weight, in the former than in the latter. In fact, "lean" and "fat'' are 

 merely vague popular terms. In a scientific sense their signification is purely 

 relative, and the percentage of fat in animals described by these terms is fortuitous. 



Both the ox and the pig eventually became fatter than the lean sheep, and 

 must, therefore, at one stage, have contained the same amount of fat. The live 

 weight corresponding to that stage is easily calculated, and, had the increase been 

 reckoned from that point, the percentage of fat in the growth-increase would have 

 been the same in all. By a similar adjustment of the live weights the growth 

 increase might have been reckoned, in each case, from the point at which the 

 percentage of fat was the same as in the lean ox or from any other stage whatever. 



The increase due to growth includes the whole of the non-fatty matter in it 

 and possibly also some of the fat, but how much is uncertain. The remainder of 

 the fat is true fattening increase. It is produced with increasing difficulty as the 

 condition of the animal improves. Does this apply, in any degree, also to the fat 

 hitherto regarded as part of the growth increase, or does the return (in shape of 

 fat) for food consumed begin to diminish only after a certain stage — e.g. the "par" 

 condition, has been reached? It seems scarcely probable that any sharp line of 

 demarcation should exist between fat formed by growth and that called true 

 fattening increase. But if it be impossible to distinguish between them, theoreti- 

 cally, then only non-fatty matter could be regarded as growth, and the absolute 

 zero of condition would be represented by animals entirely devoid of fat. That 

 such an animal does not in fact exist makes the proposition somewhat un- 

 acceptable, but does not necessarily render it untenable as a working hypothesis. 



The " par " condition — the point at which formation of protein tissue ceases in 



