116 



THE AMERICAN ENTOMOLOGIST. 



In Fig. 78 the mite has got down beneath the 

 epidermis. In Fig. 79 it has commenced dig- 

 ging the buiTOW longitudinall}', and the place 

 (/) where it was in Fig. 78 has, by the gradual 



[Fig. 78.] 



[Pig. 79.] 



[Fig. 80.] 



growth of the cells, come np nearer to the 

 surface of the skin. In Fig. 80, the point (/) 

 has thus come up to the surface, whilst the mite 

 has gone along further with its burrow. An 

 animal, when it gets on to the skin, crawls till 

 it finds a suitable soft place, ■when it tips on to 

 its fore-legs, and commences to work its way 

 ill. The female, as she progresses, lays her eggs 

 behind her in the burrow, and when exhausted, 

 dies. These eggs will be seen, in a regular 

 I'ow behind the female, in the burrow, under 

 the microscope with one hundred multiplying 

 power. It is not settled how long it takes the 

 eggs to hatch, — from seventy hours to six or 

 seven days. Propably one egg is laid every 

 day. Now, it must be remembered that the 

 skin is constantly wearing off, and as constantly 

 renewed by new growth fi-om beneath; hence, 

 as will be seen by these illustrations, the eggs 

 hatched in the furrow will come to the surface 

 in time for the animal to escape from its shell 

 when fully formed. The canals which the fe- 

 male acari burrow, have generally a serpentine 

 form, and are from a twelfth to a quarter of an 

 inch in length. They show on the surface of 

 the skin a whitish dotted appearance, the dots 

 corresponding to the eggs, — the female, as seen 

 in the cuts, being at the blind end of the burrow. 

 Ignorance or forgctfulness of this fact has been 

 the cause of the Itch-mite escaping detection. 

 There will be a little pimple or vesicle on the 

 skin over where the mite went in; and, as 

 we see from these figures, the animal is not 



there, but off at some distance deeper in the 

 skin; hence, if we open the little vesicle, or cut 

 it out, the insect escapes us. The old women 

 in Corsica, and other parts of the world, knew 

 better, and with a needle dug out the acarus 

 from the end of the burrow. A surer way of 

 obtaining it, and the whole burrow, is to clip 

 tills off with a fine pair of curved scissors, com- 

 mencing at the blind end where the mite lies 

 buried. Of course a little experience is required 

 to do this work successfully. Then, if we place 

 this little laroina of epideriais on the micro- 

 scope-slide, and a covering-glass over it, but 

 without fluid, we shall most likely find the 

 female acarus and the eggs she has laid behind 

 her. A magnifying power of sixty to one hun- 

 dred times is quite suflicient. 



After this animal had been proved to be the 

 sole cause of the disease called itch, medical 

 men thought it was always necessary to find 

 the mite to be sure that their patient had the 

 itch. From the history above given, and ex- 

 planations just made, we can see how natural 

 it was that they should so often fail in this, and 

 therefore conclude that their patient was not 

 the victim of this animal parasite ; consequently 

 he was not properly treated, and did not get 

 well — he continued to itch. Hence, to account 

 for this, and cover up ignorance, was invented 

 the "Jackson itch," the "Seven-years' itch," 

 and, lately, the "Army itch." "We conclude the 

 first did not derive its name from our former 

 President, but was only popular during his 

 reign. The second was ingenious, for if a 

 patient was told he had the " seven-years' itch," 

 he naturally concluded that he could not get 

 rid of it in less than that number of years, which 

 gave time for treatment. As time goes on, soap 

 and water, and personal cleanliness, become 

 more popular, hence the Itch-mite has become 

 less and less common. In the old New England 

 days it was the pest of the village-school, the 

 town poor-house, and the city jail. During the 

 rebellion, the great armies, on the march .and 

 in the field, of course, had no opportunities for 

 I)ersonal cleanliness, so as to prevent the con-, 

 tagion of the itch-disease, therefore it spread 

 with great rapidity by contact, and the effects 

 ©f the mite's presence in the skin would also 

 bo severe. The various army surgeons had 

 not been accustomed to any such cases; they 

 searched in vain for the insect, and, repeatedly 

 failing to discover it, finally concluded there 

 must be an itch-disease not due to the itch-mite, 

 and called it the "Army Itch." These cases 

 often were furlovighed, and, in the cities at 

 home, came under the cai'e of those who, from 



