THE LOUSE. 



459 



all died of this disorder. The use of mercury, 

 which was unknown among the ancients, may 

 probably have .banished it from among the mo- 

 derns ; for certain it is, that these animals sel- 

 dom attack any in our climate, but such as 

 from sloth or famine invite their company. 



Such is the history of the human louse, 

 which, from its connection with mankind, de- 

 serves first notice : but it would be endless to 

 describe the various tribes that go under this 

 name, and swarm upon every part of Nature. 

 There is scarce an animal, and scarce even a 

 vegetable, that does not suffer under its own 

 peculiar louse. The sheep, the horse, the hog, 

 and the elephant, are all teased by them ; the 

 whale, the shark, the salmon, and the lobster, 



who attributed it to lice, imagined; for he tells us, that 

 "they are produced in the flesh, in small pustules, like 

 tumours, which have no pus, and from which, when 

 punctured, they issue." Dr Heberden, in his Com- 

 mentaries, informs us of a similar case, which he terms 

 morbus pedicularis, but which could not be so, for the 

 same reason. He represents the insect as inhabiting 

 tumours, from which, when opened, they issue. He 

 also tells u, that in all respects they resemble the com- 

 mon louse, but in being whiier. But an observer not 

 accurately skilled in entomology, might, as Mr Kirby 

 very justly remarks, easily mistake an acarus for a 

 pediculus. 



Dr Willan has cited two other cases, which he seems 

 to think may with propriety be referred to true phthiri. 

 asis. In one of these cases, it is stated that the pediculi 

 so abounded, that two black servants had no other em- 

 ployment than that of carrying baskets full of these in- 

 sects, and throwing them into the sea. This, as Mr 

 Kirby observes, appears to be somewhat exaggerated 

 and hyperbolical. We shall conclude this part of the 

 subject, by observing, that phthiriasis must vary in its 

 types, according to the species of pediculus by which it 

 is produced. 



The facts mentioned by Cuvier, that lice abandon the 

 Spanish sailors, in a certain degree of latitude when 

 going to the Indies, and revisit them again on their re- 

 turn, and that body lice are unknown in India, are ob- 

 servations that have need of being corroborated by more 

 certain testimonies than we are yet in possession of. 

 But, if true, there would be nothing in the fact very 

 surprising. A degree of considerable heat, and a more 

 abundant transpiration, might prove unfavourable to the 

 propagation of the pediculi corporis. As their skin is 

 more tender, the influence of the air might prove detri- 

 mental to them in those burning climates. 



The disgusting fact, of these vermin being eaten, is 

 not confined to the Hottentots, the Negroes of Western 

 Africa, and the Simiae. It has been observed to pre- 

 vail among some of the American tribes, and is not un- 

 common even in Europe, as amongst the beggars in 

 Spain and Portugal. Some authors have pointed out 

 the courses which should be adopted to protect or free 

 the person from these disgusting insects. The best of 

 all, in ordinary cases, is cleanliness. Of the medical 

 uses to which these animals have been applied, it is un- 

 necessary to dilate here. No one, we fancy, of the least 

 degree of intelligence, gives any credit to such remedies 

 at present. It was imagined that their introduction into 

 the uretha of new-born infants, troubled with suppression 

 of urine, might, by the titillation which they caused in 

 that canal, force the sphincter to relax, and give pas- 

 sage to the urine. Farriers used to employ the same 

 remedy with horses in similar cases. 



The pediculi proper, are confined to men and quad- 



are not without their company ; while ever) 

 hot-house, and every garden, is infested with 

 some peculiarly destructive. Linnaeus tells us, 

 that he once found a vegetable-louse upon some 

 plants newly arrived from America ; and, will- 

 ing to trace the little animal through its vari- 

 ous stages, he brought it with him from Lon- 

 don to Leyden, where he carefully preserved 

 it during the winter, until it bred in the 

 spring ; but the louse it seems did noi treat 

 him with all the gratitude he expected ; for it 

 became the parent of so numerous a progeny, 

 that it soon overran all the physic-garden of 

 that beautiful city; and leaves, to this day, 

 many a gardener to curse the Swecb's too in- 

 dulgent curiosity. 



rupeds. The ricini, or bird-lice, to &9 feathered 

 race. 



It appears that the ancients designated under the 

 name of ricinut, those acarides, or acari, vulgarly called 

 ticks, which attach themselves to the skin of dogs, oxen, 

 &c. Degeer might, therefore, have better employed 

 another denomination for the present genus, and which 

 preceding naturalists confounded with that of lice. Ac- 

 cordingly, Dr Leach has adopted, from Herman, the 

 denomination of nirmus. 



It was by no means surprising, that the earlier natur- 

 alists did not distinguish these animals from the lice ; 

 their external physiognomy is almost the same, but their 

 organization is different in many essential points, and it 

 is evident that these two genera approximate in a natu- 

 ral series. From the consideration of their resemblances 

 and differences, and from some other facts, furnished by 

 the trachean arachuida, and the branchiopoda, we may 

 see that nature, in preserving always the same type of 

 general forms, is pleased to modify, and sometimes rather 

 abruptly, that of the manducatory apparatus, or that she 

 easily converts organs adapted for grinding, into sucking 

 organs, and vice versa. Her views in this respect are 

 subordinate to the model on which the body of the ani- 

 mal is at first formed. This consideration caused M. 

 Latreille to reject as a primary character, the division 

 of insects into two lines one composed of the grinding, 

 and the other of the sucking insects. 



The ricini live exclusively on animals of the class 

 A ves. Degeer, it is true, makes mention of a ricinus 

 found on the body of a dog; but this species M. La- 

 treille refers to pediculus, and could discover uo man- 

 dibles on it. 



These insects remain by preference under the wings, 

 about the axilla, and on the head of birds ; they attach 

 themselves there very strongly, by means of the two ro- 

 bust and equal crotchets which terminate their tarsi. 

 They multiply there sometimes, in such quantities, that 

 the birds grow considerably thinner, and may even die 

 in consequence. Care should be taken to examine do- 

 mestic birds, supposed to be infested by these vermin, 

 and often to clean out the places in which they are kept, 

 and where they are accustomed to rest. By such means 

 they may also be protected from a species of mite, which 

 multiplies prodigiously in such places, and by which 

 these domestic animals are seriously incommoded. 



The genus of the ricini is very numerous; there is 

 no bird without one or two species. Redi has figured a 

 great number of them, and though his figures are rude, 

 one may easily see how many varieties the forms of these 

 insects present. Their characters, manners, &c., are, 

 with the exceptions already stated, the same as those of 

 the lice. There is one singularity in the ricinus pavo- 

 nis, and that is, that the antennae are forked. Supple- 

 ment to the English edition of Cuvier. 



