INTRODUCTION. 59 



its quality, quantity, or mode of preparation. A very 

 rich diet predisposes to anthrax and inflammatory disorders, 

 a poor diet to anaemia and dropsies. Food materials may 

 be in themselves prejudicial either by medicinal or poison- 

 ous constituents. Mouldy fodder serves to illustrate 

 this, also the various cases of poisoning by oil cake. 

 Excess of food either causes excessive distension of the 

 stomach as in plenalvia, or, when in small quantities fre- 

 quently administered, gives rise to plethora. Deficiency 

 of food gives rise to debility and anaemia. When not 

 enough food at a time is given to an ox he is unable to 

 ruminate, thus indigestion is produced. The familiar 

 instance of choking from an uncut swede is an example of 

 ill effects from improperly prepared foodstuff. Diet 

 unadapted to the special uses for which an animal is kept 

 will frequently cause disappointment to the owner and 

 require correction by the veterinary surgeon consulted 

 about the case. An extreme instance of this may be 

 seen in pregnant animals, for the nature of the diet will 

 affect the well being of the foetus in iitero. Anaemic 

 conditions of the mother will give rise to dropsy of the 

 foetus and its membranes and perhaps to its death, 

 while not unfrequently an ergotised condition of pasture 

 grass is the cause of abortion. 



Pregnancy in itself alters the nutritive equilibrium of 

 parts, and hence predisposes to disease, especially of the 

 generative organs ; it produces important though tem- 

 porary systemic changes. The pulse beats more rapidly, 

 the amount of carbonic anhydride excreted from the lungs 

 is altered, the constituents of certain excretions, especially 

 the urine, are modified, the appetite often becomes depraved, 

 and the state of the nervous system different from ordi- 

 nary. These changes culminate in the special phenomena 

 of parturition and lactation, and with decline of the latter 

 diminishes the predisposition to disease from pregnancy. 

 The conditions of surrounding air may predispose to 

 disease. Many specific disorders originate through vola- 

 tile contagions conveyed through the air and taken up 

 through the respiratory mucous membrane ; this is termed 



