86 HJEMATOXYLON CAMPECHIANUM 



they are reddish-brown. For use in pharmacy and in other ways, 

 logwood is found in chips ; these have a reddish-brown colour, and 

 a slight peculiar agreeable odour, which has been compared to 

 sea- weed, and a sweetish astringent taste. When chewed logwood 

 imparts to the saliva a brilliant dark reddish-pink colour. 



Logwood was analysed as far back as 1810 by Chevreul, who 

 found among other substances a volatile oil, tannic acid, and a pecu- 

 liar principle on which the colouring properties of the wood 

 depend, called htematoxylin or hematin. This principle has been 

 since examined by Erdmann and 0. Hesse. Haematoxylin when 

 quite pure, is colourless or nearly so, and forms white crystals 

 either with one or three equivalents of water; it is very solu- 

 ble in hot water and alcohol, but only sparingly so in cold water 

 and ether. It has a sweet taste, resembling liquorice. When 

 exposed to the air under the influence of alkalies, haematoxylin 

 becomes red. It is sometimes found crystallised in clefts of the 

 wood. The substance known as htzmatein is produced from 

 hfematoxylin by extraction of 2 equivalents of hydrogen, a change 

 which takes place by the action of oxygen under the influence of 

 alkalies. Hsematein occurs in the form of dark violet crystalline 

 scales, which exhibit a fine green hue, an appearance frequently to 

 be noticed on the surface of logwood chips. The decoction of log- 

 wood is deep red ; acids render it paler and brighter coloured ; 

 and the alkalies give it a purplish or violet-blue colour. 



Medical Properties and Uses. Logwood is a mild astringent. 

 When given internally it speedily becomes absorbed, and may be 

 detected in the urine and stools. Its long-continued use has some- 

 times been followed by phlebitis, hence some caution is necessary in 

 its employment. It has been found useful in chronic diarrhoea and 

 dysentery, in some forms of atonic dyspepsia, and especially in the 

 diarrhoea of infants. As an injection the decoction of logwood 

 has been found of service in leucorrhcea ; and in the form of an 

 ointment prepared from the extract of logwood, it is said to be 

 useful in cancer and hospital gangrene. 



The principal use of logwood is, however, in dyeing, where it is 

 employed in the production of violet and blue colours, certain 



