THE FORMATION OF OILS IN PLANTS 137 



depends upon a variety of circumstances, which are not very 

 likely to occur under ordinary conditions of feeding, but which 

 may be found when the feeding is conducted on careless 

 lines. It happens that linseed grown in hot climates contains 

 more poison than linseed grown in Great Britain, but since 

 it is also drier, the manufacturer uses steam before pressing 

 it, thus undesignedly counteracting the poison. The extent 

 to which this takes place varies according to the details 

 of manufacture in the works concerned. There is extremely 

 little risk of adult animals in good health being poisoned. 

 So long as the seed is fed whole, or only simply crushed, 

 there is little risk of poison being formed, but if linseed cake 

 in the form of fine meal is partly mixed with warm water, 

 it remains in the form of small balls. Calves, if fed with 

 such badly made linseed mash, do not properly chew the 

 balls, but swallow them whole, so that they break up in the 

 stomach and liberate the prussic acid. Where linseed, or 

 linseed meal, is actually boiled with water, the enzyme is 

 completely destroyed. Once the enzyme has been checked 

 by the action of acid or alkali it is not able to recover its 

 old vigour. A degree of acidity equal to 10*00 normal 

 hydrochloric acid is sufficient to check the activity of the 

 enzyme. Where care is taken in the preparation of the 

 meal no poisoning cases arise. linseed, like most of 

 the oil seeds, contains no starch. 



Cotton. The growth of the cotton plant has been already 

 described, and its use for the manufacture of fibre (p. 125). 

 After the cotton fibre has been removed from the seeds, the 

 latter form a valuable part of the crop. L,ike linseed, cotton 

 seed is rich in oil, containing about 30 per cent., although 

 some varieties, especially those of Indian origin, are all 

 lower in their oil content. Oil obtained from fresh seed 

 is paler in colour than that from old seed, but the latter is 

 clarified by washing with caustic soda and cooling till 

 stearin separates out. Cotton-seed oil is not a drying oil, 

 like linseed, and is used for lubricating purposes, and for 

 replacing olive oil, butter, and other edible fats. 



Owing to the large amount of husk enclosing the cotton 



