摘要:

Judged from a statistical study, the life span of the snail is five years. Parturition occurs in summer and year classes are recognizable. Sizes of approximately 12, 17, and 23 mm. are reached in one, two, and three years respectively. Sexual maturity is reached in two years and reproduction is parthenogenetic. Some snails hibernate and some aestivate. Rest marks on shells and opercula and a limy deposit in the protoconch were studied.

ISSN:1923-4287    

DOI:10.1139/cjr40d-014

出版商:NRC Research Press    

年代:1940

数据来源: NRC

摘要:

A morphological and biological study is presented of a hitherto unrecorded member of the genusStrongyloidesfrom the golden-rumped agouti (Dasyprocta agouti), a rodent native to Trinidad, B.W.I., and northern South America. The nameStrongyloides agoutiisp. nov. is proposed for this species.Observations on the free-living development over a period of three years showed the indirect type to prevail; no seasonal variation was observed. Continuous propagation of the free-living generation of this species was not observed in faecal cultures or on artificial media.A brief résumé of the classical studies on species of the genusStrongyloidesis included, together with a summary of existing hypotheses and theories on the biology of this group. A list of species and hosts for this genus is given.

ISSN:1923-4287    

DOI:10.1139/cjr40d-015

出版商:NRC Research Press    

年代:1940

数据来源: NRC

摘要:

Five combinations of diluent, salt concentration of medium, and incubation temperature have been used to study the bacterial content of curing pickles used for making Wiltshire bacon. On representative pickles from 16 plants the highest mean count was on 10% salt agar (brine dilution) incubated at 20 °C. The lowest count was on nutrient agar incubated at 37 °C. Counts on media containing no salt, 4% salt, and 10% salt (water dilution) with incubation at 20 °C. gave intermediate values. Counts on spent pickles were higher than on cover pickles. Pump pickles showed a surprisingly high number of organisms.The analytical error attributable to diluting, plating, and counting was relatively small compared with the other sources of variance. Under certain conditions the error of sub-sampling a small jar of pickle exceeds the error between replicate plates. Sampling and sub-sampling errors were therefore the primary factors limiting the precision of the determinations.Statistical analysis of the results showed that the differences in numbers observed by the different methods were highly significant for all pickles from 16 plants, and that the bacterial content of the pickles from the different plants differed significantly over all media. The number of bacteria observed by the different methods was usually correlated, i.e., pickles from a plant showing a high count by one method usually showed a high count by the other methods and vice versa. Nevertheless, it was possible to demonstrate a significant differential response of the bacteria in cover and spent pickles to the different growth conditions used. This suggests qualitative differences in the flora of the pickles. Of the several growth conditions tested, nutrient agar at 20 °C. and 10% salt agar with brine dilutions appear to be the most suitable for demonstrating differential responses attributable to qualitative differences between the flora of different pickles.

ISSN:1923-4287    

DOI:10.1139/cjr40d-016

出版商:NRC Research Press    

年代:1940

数据来源: NRC

摘要:

Surface counts of bacteria on the ribs of bacon showed that nutrient agar containing 4% salt incubated at 20 °C. gave the maximum number. In sampling the surface of a side of bacon, it was found that the removal of the surface layer of tissue yielded more accurate values than methods based on the removal of organisms by swabs or filter paper impressions.On the average, the bacterial load on the anterior ribs was greater than on the posterior ribs. Although there were significant differences in the number of bacteria on sides from the same plant, the greatest variation was between sides from different plants.A visible growth of bacteria or "slime" becomes evident on the average when the logarithm of the number of organisms per sq. cm. exceeds 7.2. Nevertheless, certain sides may appear slimy at log 6.7 per sq. cm., while others will not show this condition at log 8.0 per sq. cm. This variation in the number of organisms present at the visible slime level may result from differences in the flora, different types of growth of the same organism, or variability in the method of detection.The number of bacteria on the side was found to be correlated with the age of the sides from cure or from packing. The growth rate is slow during the first 8 to 10 days from packing, after which it increases. Sides having an initial load of 100,000 organisms per sq. cm. at packing may be expected to remain free from slime for 20 to 25 days, if stored at 1.1 °C. No correlation was obtained between the number of bacteria in the curing pickle and the number on the product.

ISSN:1923-4287    

DOI:10.1139/cjr40d-017

出版商:NRC Research Press    

年代:1940

数据来源: NRC