摘要:

Intact embryos of speckled trout and Atlantic salmon were exposed to solutions of oxygen and nitrogen in distilled water. It was observed that as the partial pressure of oxygen was reduced a pressure was found below which the frequency of the heart-beat was not maintained at the normal level characteristic of higher partial pressures of oxygen. A "critical" partial pressure of oxygen for heart-beat frequency can therefore be said to exist. Data have been obtained from which its value at five different temperatures can be determined. The critical pressures for the two organisms are similar, rising from approximately 3 to 5 mm. of mercury at 1.5 °C. to 40 to 50 mm. of mercury at 20 °C. Possible mechanisms leading to the establishment of a critical oxygen partial pressure are discussed. It seems likely that diffusion is not the limiting factor in these preparations so that the critical pressure, and its temperature coefficient, must be the property of the intracellular respiratory systems concerned. The finding that the logarithm of the critical partial pressure can be represented as a linear function of the reciprocal of the absolute temperature is consistent with this view. Temperature exercises a more pronounced effect on the critical oxygen pressure of the pacemaking process, than it does on the over-all velocity of that process as indicated by the normal frequency of the heart. It is concluded that the critical pressure is a characteristic of the chemical systems in the pace-making cells of the heart.

ISSN:1923-4287    

DOI:10.1139/cjr42d-001

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

This parasite has been reared from larvae of the webbing clothes moth obtained from different localities as well as experimentally. All parasites obtained by natural and experimental infections were females. Oviposition occurred and parasites developed in host larvae weighing 1.6 to 6.8 mg. The parasites oviposited more readily in a host enclosed in a case, especially if the case contained fecal pellets of the host. Eggs were deposited in various parts of the host. A single parasite developed to maturity even though several eggs may have been deposited in the host, each by a separate "thrust" of the ovipositor. Morphological features of the larvae are illustrated. The rate of development varied even at constant temperature. The average length of the life cycle at 27 °C. was 26 days but at 20 °C. it required several months. Experiments were carried out to determine the factors responsible for the variation in the rate of development. The parasite larva, upon emerging from the host, usually spins a white, silken cocoon, although metamorphosis was sometimes completed even though no cocoon was produced.

ISSN:1923-4287    

DOI:10.1139/cjr42d-002

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

The pH value of the aqueous liquors derived from fish muscle tissue is connected through statistical relations with the buffer action of the liquor, the log bacterial count of the sample, and with a subjective estimate of freshness determined on the basis of odour. In the case of pH and odour rating the relation is not a correlation but, instead, a linear relation between the means of a series of populations. By means of the latter it is possible from observations of the pH of the aqueous liquor in the sample to determine objectively the freshness of a parcel of canned chum salmon to any desired degree of accuracy by increasing the size,n, of the sample taken for examination.

ISSN:1923-4287    

DOI:10.1139/cjr42d-003

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Twenty-four amphipod species (one a new species), three euphausiids, and two mysids are recorded from the coastal water of the Canadian eastern Arctic. Most of the records are new.The list is representative of a high arctic plankton, giving no evidence of the intrusion of Atlantic water. This is in agreement with the hydrographic observations made, and with available hydrographic data from other sources.The plankton is contrasted with that found in 1936 in Disko Bay, west Greenland, where there appears to be an upwelling of mixed Arctic and Atlantic water. The difference between the plankton of the two sides of Baffin Bay suggests the possibility of distinguishing water of Lancaster Sound (Canadian polar water) from that of west Greenland by means of their planktonic fauna.

ISSN:1923-4287    

DOI:10.1139/cjr42d-004

出版商:NRC Research Press    

年代:1942

数据来源: NRC