30 Mr. Children on some alvine concretions 
I must not conclude this communication without referring 
to other similar alvine concretions, which have been at differ- 
ent times met with in those parts of the country where oat- 
meal is in common use as an article of food among the poorer 
classes. Dr. Marcet, in his Essay on Calculous Disorders, 
mentions a concretion which was showed to him by Dr. Bos- 
tock, that had been voided by a labouring man in Lancashire ; 
and Dr. Marcet himself examined another given him by Mr. 
Silviera, who had it from Dr. Monro of Edinburgh. It was 
in the examination of this calculus, that the true nature of the 
velvety fibrous substance was ascertained by Dr. Wollaston, 
who, Dr. Marcet says, “ found it to consist of extremely mi- 
“ nute vegetable fibres, or short needles, pointed at both ends ; 
“ which he immediately conjectured to arise from some kind 
“ of food peculiar to Scotland. For some time, however, he 
“ failed in his attempts to trace this substance to its origin. 
“ But the ingenious Mr. Clift, of the College of Surgeons, 
“ to whom the subject was mentioned in conversation, having 
“ put the question, ‘ whether this fibrous substance might not 
“ * proceed from oats/ Dr. Wollaston was induced to ex- 
“ amine the structure of this seed ; and the result fully 
“ verified Mr. Clift's conjecture.” (p. 1 39). 
In Dr. Alexander Munro's Morbid Anatomy of the 
Gullet, mention is made of forty-two alvine concretions col- 
lected by the Author's father, which were examined by Dr* 
Thomson; Their structure, (with one exception similar in 
all) is described by Dr. Monro (p. 32) “ as more or less 
“ porous, and somewhat like to dried sponge, and when ex- 
“ amined by the aid of a magnifying glass, seems to be made 
“ up of a number of very small fibres intimately interwoven 
