BY DR. MICHAEL FOSTER. 407 



Decapitation. Introduce one blade of a strong pair of 

 scissors into the mouth, and bring it, transverse to the long 

 axis of the head, as far back as possible. Bring the other 

 blade down to the skin behind the occiput, and quickly cut off 

 the head, being careful that neither blade slips forward. 

 Simple inspection will, at once, determine whether the whole 

 of the encephalon has been removed or no. The bleeding, in 

 man 3 r cases, is excessive, and must be staunched by astringents 

 or by the actual cautei\y. Indeed, where decapitation seems 

 desirable, it is far better to employ the galvanic cauture, 

 introducing the loop of platinum wire into the mouth, and 

 bringing it out through the occiput along the line a-&, fig. 266. 



For the general study of reflex actions, division of the 

 medulla is preferable to decapitation. The large amount of 

 bleeding, the exposure to the air, and possibly other causes, 

 often lead, in the latter case, to abnormal results, ex. gr., 

 pseudo-voluntary movements on the one hand, and lack of 

 reaction on the other. 



Obs. I. Place the frog, immediately after the division of 

 the medulla, on its bell}', with its legs extended. In most 

 cases the legs will remain extended, and at first no movements 

 will be produced b3 T stimuli applied to any part of the bod}'. 

 The animal (or rather its spinal cord) is in a state of shock, 

 consequent upon the operation. 



If the animal be watched, it will be found that after a while 

 the hind legs, apparently without the intervention of any 

 external stimulus, are suddenly, first one and then the other, 

 drawn up to the body, and assume the wonted flexed posture. 

 This is a token that the condition of shock has passed away. 

 If now one of the legs be pulled out, and then let go again, it 

 will be immediately drawn up once more under the body. 



After the shock has passed away, the legs having been 

 drawn up, the animal will appear to have assumed a natural 

 posture. On observing it more closely, however, it will be 

 found that the posture is not "quite natural. The line of the 

 back is too horizontal, the head lies flat, with the neck almost 

 touching the table, and the fore limbs spread out ; whereas :in 

 entire frog keeps the head and neck raised high up on the 

 almost vertical fore limbs, and the line of the body makes a 

 large angle with the plane of the table. 



If left to itself, the frog will exhibit no movements whatever, 

 will not stir from the spot in which it is placed unless some 

 external stimulus be brought to bear upon it. This absence 

 of spontaneous movements is most marked, when sudden 

 variations of temperature are avoided, and the skin is not 

 allowed to get dry. Hence it is advisable to place the animal 

 on a dish containing a small quantity of water, and to cover it 

 with a glass sh;-de. 



