This section is from the book "The London Dispensatory", by Anthony Todd Thomson. Also available from Amazon: PDR: Physicians Desk Reference.
Syst. Nat. Gmelin, 2963.
D. 3. Articulata. Cl. 2. Ord. 1. Crustacea Decapodia, Cuvier.
Feet eight (sometimes six or ten), two of them with claws. Palpi six, nearly equal. Eyes two, distant, moveable, in many of the species standing on longated peduncles. Mandible horny, thick. Lip triple. Tail jointed and unarmed.
Sp. 27. C. Pagurus. Black-clawed Crab. Brit. Zoology, iv. 4. t. 3.
Sp. 63. C. Astacus. The Crawfish. Brit. Zoology, iv. 9. t. 15. f. 27.
1. Cancer Pagurus. Officinal. Chelae cancrorum, Edin. Crab's Claws.
Syn. Patte d'Ecrevisse (F.), Klauaan Krabbe (G.), Forbici di Granchi (I.), Pierna de Cangrejos (S.), Kreeftschaaren (Dutch), Kraftkler (Swed.).
The black-clawed crab frequents the rocky coasts of the North Sea and the British isles; and is considered delicious food. The thorax is obtusely scalloped; the body smooth; and the front five-toothed. The hind feet are subulate; but the fore are furnished with large claws tipped with black. It annually casts its shell, between Christmas and Easter.
Mr. Hatchett found that the crustaceous covering of crabs and lobsters consists of carbonate of lime, phosphate of lime, and a cartilaginous matter, possessing the properties of coagulated albumen. The first of these constituents predominates1; and it is on it that the medical properties of the claws depend. They are now deservedly rejected by every judicious practitioner, chalk answering, much better, every purpose for which they can be prescribed.
2. Cancer Astacus. Officinal. Lapilli Cancrorum, Edin. Crabstones.
Syn. Yeux d'Ecrevisse (F.), Krabsangen Krebssteine (C), Kraftsteene (Dutch), Krafstenar (Swed.), Ojos de Cangrejos (S.)•
The crawfish frequents rivers, forming its holes in their clayey banks. It is small, and in some degree resembles the lobster in shape. The snout is projecting and serrated on the sides; the thorax is smooth; as is also the back, which has two small spines on each side. The large claws are beset with small tubercles: the two first pairs of legs are clawed, the two next subulated; and the tail has five joints, with rounded fins.
1 Constituents of the shell: chloride of sodium 1.60 + phosphate of lime 6 + phosphate of magnesia 1 + carbonate of lime 62.80 + animal matter 28.60 = 100÷00.
The concretions, called eyes, are found in the stomach, one on each side, before the fish casts its shell in July, at which time the inner coat of the stomach also is renewed. They are said to be destined for assisting in the formation of the new shell. At Astracan, where the greatest number of these concretions are procured, the crawfish are bruised with mallets, and allowed to putrefy in heaps, after which their remains are washed, and the stones picked out.
Qualities. - Crabstones are whitish or reddish, hard and stony, of very different sizes, weighing from one grain to twelve grains each; round and convex on one side, and a little concave on the other : the texture is laminated; inodorous and insipid. Their constituents are the same as those of the crab's claws. They effervesce in acids; but, instead of dissolving altogether, they become soft, transparent, and retain their original form; by which means the real stones are easily distinguished from counterfeited imitations.
Medical properties and uses. - These concretions are absorbent and slightly antacid; and when prepared by trituration and levigation, are employed in dyspepsia and other diseases attended with acidity of the primae viae; but as chalk answers better in these cases, they may well be dispensed with.
The dose is 3 j. or 3 ij. suspended in a proper fluid.
Officinal preparation.-Cancrorum Lapilli prceparati, E.
 
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