FAMILY PHYLLOSTOMID.E. VAMPYRES. 187 



ture at the bottom of the cheek-pouch on each side ; these 

 apertures are furnished with a circular muscle, which prevents 

 the return of the air except at the will of the animal; and 

 large valves for the same purpose exist in the head and back. 

 The use of this singular provision is not known, unless it be for 

 diminishing the specific gravity of the body, by increasing its 

 bulk ; which seems to be at least one of the purposes answered 

 by the air-cells of Birds. 



170. The Bats of the second family, PHYLLOSTOMID^E, are 

 for the most part inhabitants of South America ; where they 

 may be regarded as representing the preceding. Although the 

 greater number of them are insectivorous, there are several species 

 which seem destined to subsist on the blood of other animals ; 

 possessing a peculiar arrangement of the front teeth for making 

 the incision ; and a conformation of the tongue, which specially 

 adapts it for suction. This is the case with the genus Desmodus, 

 which includes the True Vampyres. The upper jaw is furnished 



with two large upper incisors 

 in the centre, and two lancet- 

 shaped canines, separated from 

 them by an interval ; all these 

 teeth are extremely sharp- 

 pointed. In the lower jaw 

 there are four smaller incisors, 

 with a space in the centre into 

 which the upper ones pass 

 when the jaw closes; the 



FIG. 89 TEETH OF DESMODUS. . 



canines also are smaller than 



those of the upper jaw. By these teeth, a deep triple puncture 

 will obviously be made. The molars are imperfectly developed ; 

 and seem unfit for mastication ; and the intestine is shorter than 

 in any known animal of its size. One of these bats was taken 

 by Mr. Darwin, during his travels in South America, in the act 

 of sucking blood from the neck of a horse ; and he states that 

 the injury which horses sustain from their attacks, is due, not so 

 much to the loss of blood, as to the inflammation which the bite 

 produces, and which is aggravated by the pressure of the saddle, 



