and the Denticulatian of the Beak in certain Birds. 107 



of the same birds, which have no whiskers to comb, and an 

 Australian group, which have whiskers, but no serratures on the 

 claws, is discordant with Mr Dillon's opinion. Wilson, the 

 American ornithologist, in describing the Whip-poor-will, says 

 the pectinated middle claw is probably employed as a comb, to 

 rid the plumage of its head of vermin. He makes a similar re- 

 mark with reference to the Chuck-wilFs-widow. " Considering 

 the utility of such an instrument," says Mr Rennie, " we may 

 wonder, perhaps, that besides the herons, no other birds are 

 similarly provided for attacking those troublesome insects, which 

 often seriously injure the vigour and health of the animal in- 

 fested, and sometimes even occasion death." He then proceeds 

 to relate a case of a swallow, which, being infested with vermin, 

 " seemed instinctively courting human aid," and allowed him to 

 free it of its tormentors, after which it flew off joyfully to join 

 its companions. The case is similar to one which occurred to 

 Audubon. A hawk allowed itself to be caught and carried 

 home, sat patiently on a perch until its portrait was leisurely 

 finished, and then flew off in merry mood. In fact, it seemed 

 instinctively desirous of being represented by the artist. 



Observation and experiment can alon^ determine the use of 

 an organ ; but, on the subject in question, we are deficient in 

 facts. Wilson says the Carolina Goatsucker is often employed 

 in riding itself of vermin, by means of its pectinated claw, " at 

 least, when in a state of captivity." But Audubon, who had 

 better opportunities of observing that bird, professes entire igno- 

 rance of the use of the claw. Birds, however, which have no 

 pectinated claw, may be seen, in freedom and in captivity, 

 scratching their heads, often very assiduously, and thus the 

 pectination is not at all essential to the purpose. In the 

 deficiency of observed facts, we may sometimes have recourse 

 to analogy and reflection ; at least, the truth of an alleged or 

 supposed fact, may sometimes be settled by means of them. 



It is a fact that many birds are much infested by vermin, 

 especially about the head. It is also a fact that, in general, 

 these parasitic insects do not injure their patrons in a serious de- 

 gree, for animals much infested by them, appear to perform all 

 their functions as well as other individuals of the same species 

 less infested. When an animal becomes sickly, its vermin may 



