GEELACH ON THE ITCH AND MANGE. 171 



tioned, and Hering described and delineated under the name 

 Sarcoptes bovis, is Gerlach's Symbiotes bovis. 



The sheep scab Gerlach calls Scabies ovis dermatodectica, 

 and our author alludes to it as rare wherever sheep are pro- 

 perly attended to, but of course of serious moment when it 

 spreads unawares in a flock. It appears to be stationary in 

 Poland, and Delafond says that out of 35,000,000 sheep, 

 1 ,000,000 become yearly affected in France. The Derma- 

 todectes ovis, which we have been accustomed to call Acarus, 

 or Sarcoptes ovis, but which is clearly not in the habit of 

 piercing and burrowing the skin, is like Dermatodectes equi, 

 though differing from it in size. Gerlach has spoken at 

 length of the rapidity with which it propagates, and a rough, 

 but certainly not exaggerated statement, is furnished us as 

 follows : From one pregnant female, or from the 



1st generation, in 15 days, 10 females and 5 males are born. 



2nd ... 30 100 ... 50 



3rd ... 45 1,000 ... 500 



4th ... 60 10,000 ... 5,000 



5th 75 100,000 ... 50,000 



6th ... 90 1,000,000 ... 500,000 



The mange of the pig is due to the presence of a burrowing 

 sarcoptes, which was first discovered by Gurlt, and after- 

 wards seen .by Hertwig and Gerlach. In either case the 

 parasite was obtained from a wild boar. Sarcoptes suis is 

 much like Sarcoptes hominis and Sarcoptes equi. There are 

 several cases on record of communication of mange from the 

 pig to man. Gerlach has not had sufficient opportunity to 

 verify or negative the statement that Sarcoptes suis may live 

 on the horse, ox, sheep, and even dog. 



In alluding to the dog mange, our author attributes it to 

 the Sarcoptes canis, and he mentions that the different varie- 

 ties of sarcoptes, as we have already seen, differ little except 



