24 GENERAL INTRODUCTION 



stances by means of germ-plasm, life is passed from individual 

 to individual, and in this sense cannot be said to suffer death. 



Cell Death. According to Weismann, death has been evolved 

 for the good of the species, since in time, through wear and 

 tear, the vitality of aged individuals is lessened and it is to 

 the advantage of the species that such individuals should no 

 longer propagate or even exist. The term death has, how- 

 ever, many shades of meaning. In one sense living matter is 

 continually undergoing katabolic changes. It is continually 

 dying. The term may be applied to the whole organism or to 

 individual tissues. The first occurs when one or more functions 

 of the body are so disturbed that harmonious action of all the 

 functions becomes impossible. 



Somatic Death. The most convenient sign of somatic death 

 is the cessation of the heart beat, which, however, is not always 

 the cause of death. The death of the tissues does not necessarily 

 take place with somatic death. The nervous system dies very 

 soon; the heart lasts longer, the last portion to beat being the 

 right auricle. The smooth muscle of the intestines remains 

 irritable for three-quarters of an hour, and striated muscle at 

 times for hours. 



Some of the most important problems of general physiology 

 are as yet highly speculative in character, but most physi- 

 ologists believe that as knowledge increases they will all, like 

 the phenomena of lifeless bodies, be explained as the result of the 

 properties of matter and energy working under definite laws. 



