294 SCIENCE OF AGRICULTURE. Pakt II. 



the attainment of old age, that existence may be said to depend on the due exercise of 

 the functions which they perform. Whether animals have their blood aerated by means 

 of lungs or gills, they require a regular supply of oxygene gas. But as this gas is ex- 

 tensively consumed in the process of combustion, putrefaction, vegetation, and respi- 

 ration, there is occasionally a deficiency in particular places for the supply of animal 

 life. But, in general, where there is a deficiency of oxygen, .there is also a quantity of 

 carbonic acid, or carburetted hydrogen present. These gases not only injure the system 

 by occupying the place of the oxygen which is required, but exercise on many species 

 a deleterious influence. To these circumstances maybe referred the difficulty of pre- 

 serving many fishes and aquatic moUusca in glass jars or small ponds ; as a great deal 

 of the oxygen in the air contained in the water, is necessarily consumed by the germi- 

 nation and growth of the aquatic cryptogamia, apd the respiration of the infusory 

 aniraalcula. In all cases, when the air of the atmosphere, or that which the water con- 

 tains, is impregnated with noxious particles, many individuals of a particular species, 

 living in the same district, suffer at the same time. The disease which is thus at first 

 endemic or local, may, by being contagious, extend its ravages to other districts. 



1956. The endemical and epidemical diseases which attack horses, sheep, and cows, obtain in this 

 country the name of murrain, sometimes also the distemper. The general term, however, for the pes- 

 tilential diseases with which these and other animals are infected, is Epizooty. 



1957. The ravages which have been committed among the domesticated animals, at various times, in 

 Europe, by epizootics, have been detailed by a variety of authors. Horses, sheep, cows, swine, poultry, 

 fish, have all been subject to such attacks ; and it has frequently happened, that the circumstances which 

 have produced the disease in one species, have likewise exercised a similar influence over others. That 

 these diseases arise from the deranged functions of the respiratory organs, is rendered probable by the 

 circumstance, that numerous individuals, and even species, are affected at the same time, and this opinion 

 is strengthened, when the rapidity with which they spread is taken into consideration. 



1958. Many diseases, which greatly contribute to shorten life, take their rise from circumstances con- 

 nected with the organs of digestion. Noxious food is frequently consumed by mistake, particularly by 

 domesticated animals. When cows, which have been confined to the house, during the winter season, 

 and fed with straw, are turned out to the pastures in the spring, they eat indiscriminately every plant 

 presented to them, and frequently fall victims to their imprudence. It is otherwise with animals in a 

 wild state, whose instincts guard them from the common noxious substances of their ordinary situation. 

 The shortening of life, in consequence of the derangement of the digestive organs, is chiefly produced by 

 a scarcity of food. When the supply is not sufficient to nourish the body, it becomes lean, the fat being 

 absorbed to supply the deficiency ; feebleness is speedily exhibited, the cutaneous and intestinal animals 

 rapidly multiply, and, in conjunction, accelerate the downfal of the system. 



1959. The power of fasting, or of surviving without food, possessed by some animals, 

 is astonishingly great. An eagle has been known to live without food five weeks ; a 

 badger a month ; a dog thirty-six days ; a toad fourteen months, and a beetle three years. 

 This power of outliving scarcity for time, is of signal use to many animals, whose food 

 cannot be readily obtained ; as is the case of beasts of prey and rapacious birds. But 

 this faculty does not belong to such exclusively : wild pigeons have survived twelve 

 days, an antelope twenty days, and a land tortoise eighteen months. Such fasting, 

 however, is detrimental to the system, and can only be considered as one of those sin- 

 gular resources which may be employed in cases where, without it, life would speedily 

 be extinguished. In situations where animals are deprived of their accustomed food, 

 they frequently avoid the effects of starvation, by devouring substances to which their 

 digestive organs are not adapted. Pigeons can be brought to feed on flesh, and hawks 

 on bread. Sheep, when covered with snow, have been known to eat the wool off each 

 other's backs. 



1960. The various diseases to which animals are subject, tend greatly to shorten the 

 period of their existence. With the methods of cure employed by different species, we 

 are but little acquainted. Few accurate observations appear to have been made on the 

 subject. Dogs frequently effect a cure of their sores by licking them. They eat grass 

 to excite vomiting, and probably to cleanse their intestines from obstructions or worms, 

 by its mechanical effects. Many land animals promote their health by bathing, others 

 by rolling themselves in the dust. By the last operation, they probably get rid of the 

 parasitical insects with which they are infected. 



1961. But independent of scarcity, or disease, comparatively few animals live to the 

 ordinary term of natural death. There is a wasteful war every where raging in the 

 animal kingdom- Tribe is divided against tribe, and species against species, and neu- 

 trality is no where respected. Those which are preyed upon have certain means which 

 they employ to avoid the foe ; but the rapacious are likewise qualified for the pursuit. 

 The exercise of the feelings of benevolence may induce us to confine our attention to 

 the former, and adore that goodness which gives shelter to the defenceless, and pro- 

 tection to the weak, while we may be disposed to turn precipitately, from viewing the 

 latter, lest we discover marks of cruelty, where we wished to contemplate nothing but 

 kindness. 



