336 PHYSIOLOGY CHAP. 



are perfectly co-ordinated to the end of removing the obnoxious 

 stimulus. 



Besides these defensive acts, there are other co-ordinated 

 reflexes in the spinal frog connected with the reproductive 

 functions. Goltz observed that whenever a decerebrated male 

 frog is gently stroked on the skin of its back, it croaks as if to 

 express pleasure. In the breeding season if the back of a female 

 frog, or even the finger of the observer, is placed in contact with 

 the skin of the thorax of the male, the fore-limbs clasp the object 

 strongly and persistently, as in the normal sexual embrace. 



In mammals, too, it is possible to observe co-ordinated reflexes 

 in portions of the cord that are entirely separated from the brain, 

 for instance in the lumbar enlargement, after transection in the 

 thoracic segments. Ten days after the operation, when the effects 

 of " shock " have quieted down, the animal will pass urine only 

 when the bladder is full, or when the skin of the perineum is 

 tickled. So too, it only defaecates or performs movements of 

 defaecation when the anal orifice is tickled, and during expulsion of 

 the faeces it lifts its tail and shifts and flexes its hind-limbs as if try- 

 ing not to soil itself. If the skin of the animal is lightly stimulated 

 in the sacral region, the foot on the same side makes rhythmical 

 movements of alternate flexion and extension, as it normally does 

 in scratching. If the penis is excited by masturbatory manipula- 

 tions the phenomena of erection and spermatic ejaculation follow, 

 associated with movements or postures of the hind-limbs that 

 express voluptuous sensations. 



These and other phenomena admirably described by Goltz and 

 his pupils are co-ordinated reflex actions, designed to satisfy a 

 want or to protect some part of the body from injurious stimuli. 

 In other less frequent cases the motive of the reflex seems to be 

 preservation of the individual while the part is sacrificed. This 

 interesting group of phenomena were investigated by Fredericq, 

 and termed by him autotomy. More particularly in certain 

 insects (grasshoppers), crustaceans, arachnids, echinoderms, if a 

 limb is mechanically or chemically stimulated, it suddenly breaks 

 and drops off, so that the animal is able to escape from the pursuer. 

 The same phenomenon is also seen in certain vertebrates, as in the 

 blind-worm and green Lizard, which readily part with their tails 

 to escape capture. The fracture of the limb or tail is effected by 

 a violent reflex contraction of certain muscles by a mechanism 

 which is not fully known. Since the phenomena of autotomy 

 persist in decapitated animals they witness to a solidarity of 

 action, almost one might say a personality of the spinal cord when 

 it is separated from the cerebrum. 



Even in the absence of external stimuli, the spinal animal 

 sometimes carries out complex actions which differ little from 

 those of the intact animal. It is an ancient observation that 



