698 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



of the stomach. Numerous instances of pathological increase of nutri- 

 tive activity from increased blood supply and consequent increased tem- 

 perature will doubtless suggest themselves. 



In addition to this indirect influence of the nervous system through 

 the vaso-motor nerves on calorification, the central nervous system is 

 stated to both directly and reflexly govern the development of heat, 

 though much of the evidence brought forward as to a special nervous 

 mechanism for regulating animal heat is imperfect. Experiments have 

 chiefly been directed toward locating special heat-centres in various 

 parts of the brain. Ott claims that there are four localities in the brain 

 irritation of which increases bodily temperature bj r from 2.2° to 3.3° C. 

 These heat-centres are said to be located as follows : 1. In front of and 

 beneath the corpus striatum. 2. The median portion of the corpora 

 striata. 3. Between the corpus striatum and the optic thalamus. 4. The 

 anterior inner end of the optic thalamus. A heat-centre is also claimed 

 to be present in the dog, in the cortex of the anterior portion of the 

 upper surface of the brain, near the median line, the locality agreeing 

 with that of the motor centres of the hind limbs, and for the movements 

 of flexion and rotation of the fore limbs. According to Wood, section 

 of the brain between the pons and medulla oblongata causes increased 

 radiation of heat and diminished heat production, due to the cutting of 

 the paths of communication with the cerebral heat-regulating centre. 

 There seems to be little doubt but that irritation of various parts of the 

 brain does lead to modifications in the heat-producing mechanisms 

 of the body, and that fibres in connection with these centres decussate 

 in the medulla ; but as to whether the effects produced are stimulating 

 or inhibitory, whether they act through the production of change in 

 circulation, or whether they directly influence the chemical operations 

 concerned in the production of heat, is quite unknown. 



