6 CASSAVA. 



anatysts are in general accord. It is usually held that sweet varieties 

 contain only half as much prussic acid as those known to have been 

 fatal, and also that there is no distinct dividing line between the two, 

 but a gradual merging of one into the other. 



Carmody suggests that the difference between the two varieties con- 

 sists in the hydrocyanic acid being distributed throughout the bitter 

 kind, whereas in the sweet variety it is principally found in the cortex. 

 His results show, however, that peeled sweet varieties contain from 

 0.003 to 0.015 per cent of hydrocyanic acid and peeled bitter varieties 

 from 0.014 to 0.042 per cent, with practically no difference between 

 the two kinds in the composition of the cortex, from 0.014 to 0.042 

 per cent of hydrocyanic acid being found in the cortex of both. 



In a series of results obtained- by the Jamaica analyst on tubers 

 grown in Colombia, the mean percentage of hydrocyanic acid in 

 seventeen varieties is 0.001, the maximum being only 0.003. This is 

 in marked contrast to the previously determined mean of the Trinidad 

 sweet varieties, which was 0.016 according to Francis and 0.010 

 according to Carmody. From these results it is concluded that all 

 Colombian varieties are practically sweet, and this view is supported 

 by a note to the effect that in the interior of Colombia the people do 

 not know of the existence of poisonous varieties. 



The analyses of three bitter varieties made in Jamaica (Cousins) 

 show from 0.036 to 0.077 per cent of total hydrocyanic acid. In a 

 series of twenty-five varieties the same analyst finds from 0.010 to 0.077 

 per cent of this poison, and in a third series six bitter varieties are 

 found to average 0.018 and six sweet varieties 0.001 per cent. It is to 

 be noticed that these bitter varieties are but a trifle higher in hydro- 

 cyanic acid than the mean of 0.016 obtained by Francis for sweet 

 varieties at Trinidad. 



Upon another occasion the Trinidad station sent to Jamaica for cut- 

 tings of their best varieties of sweet cassava and an analysis made of 

 the tubers by the Trinidad analyst (Ince) gave 0.001 per cent of hydro- 

 cyanic acid present. In the report from Trinidad the question is 

 raised as to the possibility of sweet varieties degenerating into poison- 

 ous varieties and the opinion is stated that certain varieties unques- 

 tionably undergo this change, the hydrocyanic acid content being to 

 some extent dependent upon environment. The same station notes 

 that residents of Colombia who have imported bitter varieties from 

 Jamaica find that they become sweet. 



METHODS OF ANALYSIS. 



In considering the results discussed in the preceding pages, and in 

 view of recent investigations, it is of peculiar interest to review the 

 methods employed for estimating hydrocyanic acid at the Trinidad 

 and Jamaica stations. 



