Natural History. 493 



5. Production and Preparation of Pearls. — For Mr. Gray's ob- 

 servations on the artificial production of pearls, see p. 167, vol. xix., 

 and p. 412, vol. xx., of the first series of this Journal. M. Geiger 

 has made some experiments upon these substances : one object was 

 to ascertain the probability that the Persians caused birds to swallow 

 the pearls for the purpose of removing the crust with which their 

 surface is sometimes covered. From the trials made with two cocks, 

 M. Geij^er thinks that the practice may be rendered useful : he 

 thinks also that the formation of pearls is always due to the intro- 

 duction of extraneous bodies into the shells of the fish ; he believes 

 that they may be made artificially, with advantage, and. is told that 

 fine pearls are made in Finland in this manner. — Bidl. Univ, 

 C. X. p. 178. 



6. Peduliar Cases of the Use of Milk as Food. — A giraffe, which 

 was sent to the King of France by the Pacha of Egypt, was observed 

 never to drink the smallest quantity of water, but only milk. This 

 odd circumstance is explained by the person who describes its habits 

 and manners, as resulting from the circumstance that being taken 

 whilst young, it was, probably, supplied with milk, which not having 

 been discontinued, has occasioned this permanent inclination in the 

 animal. It appears very probable, that animals which drink but 

 little naturally, will not drink water, if a sufficient quantity of milk 

 be supplied to them. Milk was offered to two young asses which 

 had been separated from their dam for some time, and they dranlc 

 it with pleasure. It was then offered to a young mule, and to a 

 horse five years of age; both drank of it. Being offered to a monkey, 

 it seemed never to have taken enough. Pigs, dogs, cats, and rats, 

 drink milk with avidity. '* I will quote on this occasion a curious 

 fact, but little known, — that of a goat which sucked itself, and which 

 was, with difficulty, broken of this bad habit." Now, as there are 

 so many animals which like milk, without having preserved the habit 

 of drinking it, it will not seem surprising that the giraffe, a her- 

 bivorous animal, which has been continually supplied with this 

 drink, should prefer it to all others.— Mem. du Museum, xiv. p. 74. 



7. Preparations of Henbane and Belladonna, by M. Buchner.— 

 M. Buchner prefers the well-prepared extracts of these plants in 

 practice, to the purified and peculiar principles in their crystalline 

 forms. His process for preparing the extracts, consists in pulveris- 

 ing the plant, and digesting it in alcohol of a specific gravity of .847 

 for several hours ; the liquid is then to be filtered, distilled until two- 

 thirds have passed over, and the residue evaporated until of the 

 consistence of extract. It is then to here-dissolved in water, filtered 

 and re-evaporated to dryness. The extracts thus obtained are of a 

 yellowish colour, transparent in thin plates, possessing the odour of 

 the plant,. and soluble in water and alcohol. 



Dr. Reisinger, who has employed these preparations, concludes 



