Vol. XVII. No. 416. 



THE AGRICULTURAL NEWS, 



103 



value of the cereals, and not far from twice that for average 

 lean meat. 



Professor Jaffa says that it would appear that, as far 

 as fruits are concerned, the avocado is in a; class by itself, 

 containing on the average a far higher caloric value than 

 any other fresh fruit except the olive. 



It must not be assumed that the avocado has a total 

 food value greater than that of lean bi'ef. It is only the 

 caloric values which are compared, and much of the value 

 of meat as a food lies not in the energy that it produces, but 

 in its ability to build up and repair the used up ti.ssues of 

 the body. ' 



The presence of such a large percentage of oil in the 

 avocado has suggested that this fruit might yield a table 

 or cooking oil which would be as valuable as olive oil, peanut 

 oil, or other products of this nature. The Bureau of Chem- 

 istry of the Department of Agriculture, United States of 

 America, has extracted from the avocado a thick white fat 

 which strongly resemble.s some of the cooking fats now on 

 the American market, and A. C. Hagemanh of New York 

 was able to extract from avocados grown in Florida a green 

 oil very much like olive oil in character. 



The extraction of oil from the avocado is a subject which 

 may possibly receive much attention, for it is possible that 

 the large quantities of avocados annually (produced in the 

 American tropics might be utilized for tliis purpose. 



In comparing the possibilities of tlie avocado with the 

 olive as an oil producer, Mr. Popenoe calculates that 

 assuming that .50 per cent, of the oil in tbq fruit be lost in 

 extraction, 48 gallons of oil would be tlie Average product 

 per acre Irom avocado trees, which is practically the same 

 as the average obtained from the olive in California to-day; 

 but, considering that the calculations are based on the 

 percentage of oil contained in the Trapp variety of avocado, 

 which is not quite 10, while in some other varieties it is as 

 high as 30, there is evidently a possibility of jgetting more oil 

 from avocados than from olives. 



No commercial extraction of oil from the avocado has 

 been undertaken as yet, and the calculations, though based 

 on actual figures obtained in Florida avocado groves, and on 

 laboratory analyses of the fruit, are not to be considered as 

 anything more than suggestive of the possibilities of this 

 fruit in a very important line, the production of oil. 



FOOD-BORNE INFECTIONS. 



An address on the above subject delivered by Dr. Edwin 

 O. Jordan to the American Association for the Advance- 

 ment of Science, at Pittsburg, in December 1917, is given at 

 length in Science, January 2-5, 1918. Some interesting extracts 

 from it are given below. Dr. .Jordan .says that not long ago 

 the majority of attacks of gastrointestinal disturbance, 

 traceable to some food eaten shortly before, were declared 

 due, to ptomaine poison, and were deemed to be sufficiently 

 explained by this designation. It was believed, though 

 hardly on very good evidence, that the foods responsible for 

 the trouble had been kept too long or under improper 

 condition, and had undergoua bacterial ilecpmposition. This 

 decomposition was supposed to have resulted in the formation 

 of ptomaine, a name given to certain compounds formed in 

 the later stages of protein disintegration. 



Confidence in this theory has been shaken by many facts. 

 For one thing, ptomaines are formed in the later stages of 

 protein decomposition, and there is little doubt that food 

 containing ptomaines would almost invariably be condemned 

 by the senses as nauseating and unfit for use. Perhaps 



the principal reason however for the decline in the belief 

 that ptomaines have any important share in the production 

 of food poisoning has been the discovery that in 

 many instances the responsibility can be placed definitely 

 upon other factors. The outbreaks of food poison- 

 ing that have been most thoroughly investigated have 

 been found to be due, not to the use of spoiled food contain- 

 ing ptomaine, but either (1) to the presence of true bacterial 

 toxins comparable to the toxins of the diphtheria and tetanus 

 bacilli and not to be regarded as the simple product of 

 decomposition, or (2) to infection with specific bacteria borne 

 in or upon the implicated food. 



Poisoning from bacterial products in food, when it occurs 

 at all, seems to be due to the accidental and occasional 

 presence of toxigenic microbes which give rise to specific 

 toxins. Little is known about the condition under which 

 the relatively rare toxigenic bacteria find their way into 

 foodstuffs. All told, demonstrated instances of food 

 poisoning due to bacterial products are not very numerous. 



On the other hand, the careful investigation of food 

 poisoning outbreaks has brought to light a very large number 

 of instances of apparent poisoning, which are in reality 

 due to infection with some pathogenic micro-organism. 



In general micro-organisms pathogenic for man do not 

 increase freely outside of the human body, but in many foods 

 conditions obtain very much like those in the artificial culture 

 media used in laboratories. There are many instances where 

 the incriminated food when fresh gave rise to little or no 

 injury, but after standing twenty-four hours or less, without 

 visible signs of decomposition produced numerous cases of 

 illne.ss. There can be little doubt that the almost universal 

 preference tor fresh food rests on a sound physiological basis. 



Thorough cooking, including adequate pasteurization of 

 milk, is probably the best meins of preventing all forms of 

 food-borne infection. 



MINERAL OIL RESOURCES IN THE 

 BRITISH EMPIRE. 



Some interesting facts about the production of mineral 

 oil within the British Empire were given by Professor J. S. 

 S. Brame, of the Royal Naval College, in a recent lecture 

 before the London School of Economics. In the present 

 circumstances such sources are specially valuable, as being 

 less liable to interruption than these in foreign regions. By 

 far the most important source of supply is Burma, which 

 furnishes nearly 3 million gallons per annum. Assam and 

 the Punjab also afford useful contributions, while among 

 other regions may be mentioned Taranaki in New Zealand, 

 Trinidad and Barbados, Canada, Egypt, Sarawak, and British 

 North Borneo. In Canada the output has unfortunately 

 diminished during recent years. Within the United Kingdom 

 the Scottish shale-oil industry is an important asset, and 

 further possible sources in Norfolk and elsewhere are being 

 examined. There are vast latent possibilities in the distil- 

 lation of oil from the tar fields of Athabasca, which extend 

 over thousands of miles, and probably cantain enoagu oil to 

 last the world for 2,000 years. When the country is more 

 fully developed, better transport facilities available, and 

 the cost of extraction reduced, the.se deposits may 

 prove a very valuable asset to the Empire. At present, only 

 about 3 per cent, of the world's production of mineral oil 

 comes from the British Colonies and Dominions. 



The foregoing information is gleaned from the Journal 

 of the Jioya/ Sfcie/y of Ans, February 8, 1918. 



