462 Journal of Agrictdture. [8 August, 1907. 



the manager's time has been taken up in showing them round and ex- 

 plaining methods. It must not be imagined, however, that visitors are 

 unwelcome ; the main object of the farm is to demonstrate certain things, 

 and inspection will teach more, far more, than mere printed reports. 

 Consequently visitors are always welcome. 



It cannot be said that the past year's operations have yielded much 

 from an irrigation point of view. Inabilitv to obtain water at the right 

 time precluded useful experiments. What has been done, however, is 

 .to show the settlers the value of rape and mangold crops, the use of 

 silage and its advantages, the preparation of land for irrigation, and 

 utility of a traction engine upon a farm with operations big enough to 

 justify its employment. The manager has proved himself in this first 

 year an indefatigable and practical worker, a keen enthusiast as to the 

 results of irrigation, and has evinced much tact in arousing the interest 

 of the settlers on the estate. To him much of the success which is 

 confidently anticipated will be due. 



THE ELEMENTS OF ANIMAL PHYSIOLOGY. 



W. A. Osborne, M.B., D.Sc, Professor of Physiology and Histology, 

 Dean of tJie Faculty of Agriculture in the University of Melbourne. 



{Continued from page 346.) 



CHAPTER VIII. 



Animal Heat. 



It has long been recognised that from the stand-point alone of tempera- 

 ture animals can be divided into two great groups. The popular terms 

 for these groups namely cold-blooded and warm-blooded are based upon 

 very profound differences, but they are not too well chosen, fo' a so-called 

 cold-blooded animal, say, a snake, may occasionally have a temperature 

 exceeding that of a so-called warm-blooded animal, say a man or a horse. 

 The true distinguishing point is this that, in one class, the temperature of 

 the animal is never far removed from the temperature of the environment, 

 and that it varies within wide limits and parallel with the changes in 

 temperature to which the animal is exposed. The temperature of such an 

 animal is in fact determined by the temperature of the environment in 

 which it lives. Such an animal we may call an animal of variable tem- 

 perature or, to use the technical adjective, a poikilothermal animal. But 

 when we examine a bird or a mammal we find that its temperature varies 

 within extremely narrow limits, is independent of ordinarv changes in en- 

 vironment and has a marked tendency to remain constant. Birds and 

 mammals are therefore constant-temperature animals or homoiothermal. 

 The homoiothermal animals by virtue of their constant temperature possess 

 manv advantages over the poikilothermal. It has already been stated that 

 the activities of all cells increase or decrease as the temperature of the 

 cells rises or falls. Thus it is that a lizard is active on a warm dav but 



