326 PHYSIOLOGY AT THE FARM. 



name tapioca is commonly applied. It obtains this form by 

 being dried on hot plates. The heat thus applied breaks the 

 starch globules and renders them partially soluble in cold 

 water ; whence an infusion of tapioca in cold water after 

 filtration gives a blue colour with iodine. Boiling water 

 renders tapioca gelatiniform, tremulous, viscous, and trans- 

 parent. It is purer than sago, owing to the absence of colour- 

 ing matter. It affords a more consistent jelly than most 

 other kinds of starch. 



Cassava. Cassava is derived from the same plant, and is 

 extensively used for bread in Brazil, Guiana, and Jamaica. 

 The roots of the JatropJia manihot are washed and scraped 

 clean, they are then grated into a trough and afterwards sub- 

 jected to pressure in a hair bag. The expressed juice of the 

 roots of the JatropJia manihot are believed to be dangerously 

 poisonous, but the treatment to which they are subjected 

 affords a starch which, whether in the form of cassava or 

 tapioca, is perfectly innocuous. 



The name applied to the plant which furnishes tapioca and 

 cassava by Linnaeus is Jatropha manihot, and this is still its 

 most common name in works on dietetics ; but it has also been 

 called Manihot utilissima, and from a native American word 

 Janipha manihot. 



Arrowroot. The name arrowroot is given to a very pure 

 white amylaceous powder imported from most of the West India 

 Islands, but particularly from Bermuda, that from the latter 

 place being most esteemed. It makes a rather stiff jelly, and 

 has the advantage of being entirely free from colour and from 

 any disagreeable flavour. It is obtained from the roots of the 

 Maranta arundinacea. It was called arrowroot because its 

 fleshy root was believed to possess the property of extracting 

 the poison from wounds inflicted with the poisoned arrows of 

 the Indian tribes. 



