62 OBSTETRICAL FHYSIOLOGY. 



The Cat is in this state in January and February, and also in the 

 spring and autumn ; sometimes the heat appears three or four times 

 a, year, and the animal may produce young as frequently ; though in the 

 wild state it seldom does so more than twice a year. 



The Pig manifests rutting in October or November — at least that is 

 the period when it is usually put to the male ; and it may be put a 

 second time towards the end of spring, in order to have two litters 

 within the twelvemonth. 



ThQ frequency and duration of the period of "rutting" or "heat" 

 •depend upon age, species, and other circumstances ; but it may be 

 said to persist in the domesticated animals from one to fifteen days at 

 the most. The shortest period is witnessed in the Cow and Sheep, and 

 the longest in the Bitch. It is sometimes only present from twelve to 

 twenty-four hours in some non-fecundated animals. With impregna- 

 tion, however, it ordinarily ceases until after parturition ; and if 

 impregnation does not occur, it gradually disappears until the next 

 period, which is somewhat variable. Its re-appearance in the Cow 

 has been noted every month or three weeks, and sometimes at closer 

 intervals ; and in the Sheep and Pig it lasts for one or two days, and 

 again appears from the fifteenth to the thirtieth day, but usually every 

 month. When removed from artificial conditions, it is stated that 

 the Ovine species is in rut in September, that this persists only for a 

 day, but re-appears every fourteen days until the end of December. 

 From the spring until the end of summer, it may be said the Mare 

 manifests a desire for the Horse every three or four weeks, and the 

 objective phenomena which announce it continue from two to four days. 

 In the Bitch they last for nine or ten days, and, as has been stated, 

 only ajjpear in the spring and autumn. 



This periodicity is regulated by Nature, with a view to the preserva- 

 tion of species ; and in animals not influenced by artificial conditions, 

 it is so arranged that the young creatures may arrive during the season 

 when their maintenance will be best assured. 



With the subsidence of venereal excitement in unimpregnated animals, 

 there succeeds a period of calm, which is almost equivalent to that of 

 gestation in impregnated creatures. And, strange to say, with Bitches 

 at the end of this interval — from the fortieth to the sixtieth day — there 

 sometimes appear phenomena allied to the parturient period ; these 

 are : tumefaction of the mammary glands, followed by swelling and 

 increase of the opening of the vulva, with reddening of the vaginal 

 mucous membrane and the escape of a viscid fluid. The animal also 

 acts as if about to bring forth — making a bed for her young ; moving 

 about uneasily ; neglecting her food for three or four days, during 

 which the mammae become still more developed, firm, and elastic, the 

 teats elongated, and the lactiferous sinuses filled with an abundance of 

 good milk, which is easily obtained by slight pressure. If a Bitch in 

 this state is presented with a young Puppy, she will take to it as if it 

 were her own, and rear it most aflectionately. This strange condition 

 has been observed, though more rarely, in the Cat ; and Chauveau has 

 also noticed it in a Mare which had been put to the Horse, but did not 

 prove in foal. 



The years during which tt'strum continues varies with species, and 

 particularly with regard to the age they attain ; but it always disappears 

 towards the decline of life. 



Climate, inseparable from the conditions of alimentation, exercises a 



