There is a very obvious distinction between intestinal calculi, seized by almost all writers on the subject, in regard of their origin : (I.) some originate elsewhere, and make their way into the alimentary canal ; (2.) others are the result of the deposition within the intestines of certain materials around some substance acting as a nucleus, itself either introduced from without or from some other part of the system; (3.) others are wholly formed in the alimen tary canal.
(1.) a, Biliary calculi, to be presently de scribed, form the great majority of those be longing to the first class. They present pre cisely the same characters as while still in con nection with the biliary system. b. Calculi sometimes pass into the intestine from the urinary passages. Dr. Marcet found a calculus, mainly composed of a mixture of phosphate of lime and triple phosphate, in the rectum of an infant with imperforate anus. A communica tion existed between the bladder and rectum.
(2.) Calculi belonging to the second class vary much in respect of their nucleus ; the matter found in the intestine, constituting the cortex of the calculus, is generally composed of phosphates, applied in layers or not, and mixed or not with additions of the vegetable or other substance which served originally as the nu cleus ; the mass is solid and compact, or softer and more porous, and mixed with the mucous secretion of the bowel. The division into layers is sometimes very indistinctly marked ; gene rally a slight difference of colour exists in the different strata. Yellowish brown is the most common hue.
The nucleus in this class of calculi may be animal, vegetable, or inorganic.
(a.) Animal.— Under the name of egagro piles, or hair-balls, have been described masses or not uncommon occurrence in the intestines of the lower animals (especially of calves), composed of hairs in their central part, in their outer parts of concrete animal and saline matter. The hairs forming the nucleus are swallowed by the animals when licking them selves. Laugier* has very carefully described a felty-looking mass of some size found in the human rectum, the cortex of which consisted of fteces, hydrochlorate of ammonia and lime, phosphate of lime, silica, and oxide of iron ; the nucleus, prismatic in shape and covered immediately with a brown crust, consisted in its central part of gelatin, in its more external of blood. Probably, as has been suggested, the mass originated, in consequence of a vessel being wounded by a piece of bone, — blood being effused round this, and saline matters subsequently accumulated round both.
(b.) Vegetable.— Nuclei of vegetable matter are more common. In graminivorous animals intestinal calculi of this kind sometimes acquire vast size. - In a horse (aged 17 years) a mass was found having a nucleus of oat-grains, and so huge as to measure 28 inches round, and weigh 19 pounds (Breschet). Laugier and Lassaigne, in a similar mass, collected round bits of straw, found the cortex composed of earthy phosphates. In the duodenum of the human subject Andral discovered a calculus of the size of a small egg, consisting of earthy looking matter externally, and having a plum stone for its nucleus.
But the most interesting calculus of this species is endemic in Scotland, and for its full history we are chiefly indebted to the investi gations of Wollaston and Dr. Monro Tertius.* The vegetable substance acting as the nuclear basis of' the mass (which looks like felt or coarse sand) is the husk of' the oat-seed in fragments, along with the minute fibrils, form ing a velvety mass at one end of the seed un derneath the husk. The abundant use of oat meal in North Britain, as an article of food, explains the frequent occurrence of these calculi among the population ; they are said by Dr. Maclagan t to be growing less common, in consequence of the greater care now be stowed in the north in separating the husky matters in preparing grain for the market. The inorganic constituent associated with the vegetable fibrous matter is mainly phosphate of lime (20 per cent. in two specimens ana lyzed by Dr. Maclagan), associated with silica, evidently derived from the oat (6 and 4 per cent.).
(c.) Inorganic. Certain medicines, magne sia (Monro) and chalk especially, have occa sionally collected into calculous masses in the large intestine of persons in the habit of swal lowing large doses of either for a considerable time : the saline matter being hardened into a solid ball with mucus and fweal matter. Croc kelt I relates the case of a child who swallowed a pin, and at the age of 18 voided per anum a calculus of spheroidal shape and earthy com position. The head and half the stem of the pin were enclosed in the mass. A piece of wood accidentally forced into the rectum has been known to form the nucleus for phos phatic deposition.§ Females who chew and swallow the ends of threads used in sewing, or indulge in the singular habit of eating their curling-papers (hysterical pica), occasionally become the subjects of intestinal calculi.