150 
Sarcoptes of Man 
the mould had invaded the preparation after it was made conidiophores would 
be found only at the edge of the cover glass. I can find no previous reference 
to the occurrence of Aspergillus in the crusts formed in this disease, and one 
or two leading dermatologists whom I have consulted inform me that they 
are not aware that it has been previously recorded. We may be dealing with 
an accidental infection of the crust by a common saprophytic mould. In 
support of this Dr Aldo Castellani informs me that Aspergillus is extremely 
common in old scrapings of a number of skin diseases. On account of this it 
was believed for many years that the causative agent of Tinea imbricata was 
an Aspergillus. We must not dismiss altogether the possibility that Norwegian 
crusted scabies is a condition produced by a secondary infection of a case of 
ordinary itch with Aspergillus. Writers of most modern text-books of der¬ 
matology (Hyde and Montgomery, Hartzell, Sutton, Sequeira), regard the 
crusted variety as common scabies occurring in a dirty and negligent individual. 
I am inclined to agree with them and to explain the minute differences between 
the common Sarcoptes scabiei and S. scabiei var. scabiei-crustosae as adapta¬ 
tions of the variety to its environment. Incrustations, similar to those of 
crusted scabies in man, are common on mangy horses; but I am unable to 
find any difference between mites from a horse which had been covered with 
crusts for many weeks, and mites from milder cases. 
The view is also held that S. scabiei var. hominis and S. scabiei var. scabiei- 
crustosae are distinct organisms producing essentially different diseases: this 
was the view held by Furstenberg and by Canestrini and Kramer. Against this 
view one may urge the minuteness of the morphological differences between 
the species and the variety. Beatty’s second case (1915) was believed to have 
been infected from a case of common scabies. Moreover Norwegian crusted 
scabies is such a rare condition that were its causative mite really distinct 
from S. scabiei var. hominis it would long ago have become extinct. Norwegian 
crusted scabies is a rare disease. It is much to be desired that some one who 
is fortunate enough to see a case should infect a few volunteers in order to 
discover whether ordinary itch or the crusted variety is induced, and whether, 
after one or two generations, the mites can in any way be distinguished from 
typical S. scabiei var. hominis. A search should also be made for moulds. 
A third view has been held, that Norwegian crusted scabies is due to an 
infection of man with a Sarcoptes derived from some other animal: Megnin 
attributed it to S. lupi. The Sarcoptes of several of the common domestic 
animals (notably S. scabiei var. eqai) produces in man a disease less, and not 
more, severe than ordinary human scabies. 
An anomaly in chaetotaxy. 
Fig. 9 shows an abnormality in the setae of an ovigerous female of Sarcoptes 
scabiei var. hominis collected by J. E. M. Mellor from our laboratory assistant 
Mr Reid after he had been artificially infected from a military case of scabies. 
The anomaly occurs on the left side only and consists in the reduplication of 
