Vol. I. No. 1. 



THE AGRICULTURAL NEWS. 



with). This is open at the top. About a foot froin 

 the top the chamber is divided horizontally into 

 two eonipartments by a sheet of iron, (B. ) and below 

 this division a small fire grate (C.) is constructed ; at 

 the opj)osite end from the gi-ate a chimney (D.) is 

 ]>!aced to lead the smoke from the lower comjjartment. 

 (Fig. 2.) In order to obtain an even heat in the ujiper 

 (• Miijiartmcnt it is well to spread a layer of sand, one or 

 two inches thick, over the iron plates. The frames 

 cirrving the coagulated milk are placed on the top of 

 the chamber, so as to form a lid or cover to the opening 

 (A.) when heat from the iron plate drives oif the mois- 

 tui'c at a low temperature. 



It is important that the temperature at which 

 drying is efiected shall be as low as po.ssible. Any over- 

 heating destroys the active principle, so that a careless- 

 ]y prejjared product may be useless. In practice, the 

 tem])erature is kept as low as is c(msistont with getting 

 the substancL' dried before deconijjO.sition sets in: if 

 this can be done without the temperature of the tray 

 beins: raised above 100 deg. Fahrenheit so much the 

 better. 



As the substance becomes dry it shrinks consider- 

 abl}- in bulk. The contents of several tra^s may now 

 be emjjtied into one and the drying continued. The 

 trays emptied are ready to receive another day's supj^ly 

 of fresh material. 



Drying must be continued until the substance is 

 cris]) and in such a condition that it can be reduced to 

 a tine ])()wder without any difficulty being e.xpi'rienced 

 from stickiness. The dried material should be ground 

 to a fine powder when the resulting product should be 

 a white or cream coloured powder with a characteristic, 

 b;it not putrid, smell. The powder .should be packed 

 in tins or bottles, and carefully j)reserved from contact 

 with the air. Grinding is easily effected in a mill of 

 the type comnKjnly employed for grinding coffee : when 

 grinfling it is desii-able to have the pajjain slightly 

 warmed. 



CASSAVA POISONING. 



Amongst the important food plants cultivated in 

 the West Indies is the 'Cassava' or 'Manioc' (Mavihol 

 utUls.Hinui, amember of the Spurge Order, or Eiipliorbiti- 

 criir), gnjwn for the .sake of the store of starch contain- 

 ed in its long, thick roots. Two kinds of cassava are 

 commonly recognised, the 'bitter' and the 'sweet,' and 

 sometimes considered to be two distinct species of 

 jtlants. Bitter and sweet cassava are put to separate 

 uses. From the bitter variety, after grating and 

 careful expression of the milky juice, a flour is obtained 

 from which thin cassava cakes are made. It is also the 

 source of ' farine' and the tapioca of commerce. Tlie 

 raw juice cooked and concentrated is known as 

 casareep. The sweet cassava is more couuuonly 

 eaten, as a vegetable, after boiling or roasting. Bitter 

 cassava in the fresh condition is well known to be 

 liarmful and experiments have been made which prove 

 the extrrmely poisonous character of its milky juice. 

 The poisonous constituent of the raw juice is prussic 



acid, or hydi'ocyanic acid, easily recognizable by what 

 is known as the 'snu'll of bitter almonds.' Prussic acid is 

 fortunately a poison which itis conij)aratively ea.sy to get 

 rid of completely. It is only n^'ccessary to ensure that 

 the substance containing it shall be thoroughly heated, 

 and all the prussic acid present is destroyed and the 

 substance rendered perfectly harmless. 



As already said, bitter cassava is universally 

 regarded as a poison(jus substance. With regard to 

 sweet cassava, on the other hand, opinions vary and 

 even in a standard book of reference on Chemistry it is 

 stated that 'the milky juice in the sweet variety is 

 innocuous, whilst that in the bitter is highly poisonous.' 



Deaths fi'om eating improperly prepared sweet 

 cassava occur from time to time in the West Indies, 

 principally amongst baflly-fed or neglected children. 

 In order to prevent, if possilile, the recuiTence of such 

 accidents, it is desirable that the actual facts should be 

 ])uljlished anfl made widely kn(jwn in the hope that 

 teachers and others may be able to put children on 

 their guard against the danger of eating sweet cassava 

 unless care has been taken in its preparation. 



As long agL> as 1877, Professor Francis, then 

 (lovernment Chemist at Trinidad, stated, as the results 

 of experiments that sweet cassava root contained 

 considerable quantities of prussic acid. His work has 

 recently been repeated and extended by his successor 

 Professor P. Carmody (Anniud RcpJii of the Govern- 

 innif Aiiiih/Nf, Trinidad, 1901, p. 15). From their 

 investigations it appears that sweet cassava not only 

 cijntains the poisonous jjrussic acid, but contains nearly 

 as much as liitter cassava, and that by mere chemical 

 analysis it woukl be impossible to distinguish between 

 the two. Professor Carmody was able to show that 

 whilst in bitter cassa\'a the prussic acid is flistriliuted 

 more or less uniforndy throughout the tissues of the 

 root, in the sweet cassava it is located chiefly in the 

 skin and outer portion of the rind. It follows that in 

 order to prepare sweet cassava so that it may be a safe 

 food for human beings the following precautions should 

 be taken : — 



(1) Carefully scrtipe off the skin and outer portion 



of the rind, whereby the greater j^ortion of 

 the poison will be removed. 



(2) Thoi-oughly heat the remainder by boiling or 



otherwise, so as to destroy and drive oft' any 

 remaining prussic acid. 



Thus prepared s^\eet cassava is a thoroughly wholesome 

 article of food, as the experience of many who eat it 

 regularly is sufficient to prove. 



One other word of warning is necessary. Profes- 

 .sor Carmixly has indicated that although all the prussic 

 acid originally present in the root may be got rifl of it 

 is possiblt' that a small further quantity may be formed 

 later bj' changes dependent on the addition of water. 

 Cassava which has been cooked and then kept for some 

 time may still be a dangerous substance, and should 

 not be eaten. The rules to be followed in preparing 

 and eating sweet cassava are thus: — (1) Scrape the 

 root. (2) Cook it wc^ll, so as to heat it throughout. 

 (3) Eat cassava only after it has been freshly cooked. 



