398 JOHN LINCK ULRICH 



even for some supposed definite reason, to produce the " success- 

 ful' ' movement. 



The functional condition of the rat can be determined only by 

 close observation of movements that produce solution of the latch- 

 box problem, and those that do not. Some data may be had 

 from conditions that make the problem difficult to solve. It can- 

 not be too strongly emphasized, that from observations of the 

 ineffective movements produced, as well as of the movements 

 that produce solution of the problem, a real understanding of 

 the functional condition of the reflex mechanism required to 

 solve the problem is to be had. Negative as well as positive 

 results then, become for a tune our chief concern, for we arrive 

 at qualifications that are necessary both for the solving and for 

 the learning of the latch-box problem. 



To solve the latch-box problem, in addition to sensory excita- 

 tions to produce the neck reflex, other reflex parts are necessary to 

 produce posture, in order that an adequate neck reflex move- 

 ment can be produced. The first evidence of posture is a crouch- 

 ing followed by a setting of the body. The setting of the body 

 appears to be a momentary fixed position or a contraction of the 

 extensor muscles of the entire body before the body is raised with 

 the production of the neck reflex movement. With some rats, 

 posture seems to be adequate when the neck reflex is readily 

 performed, and then the crouching and setting of the body are 

 not excessive. With some rats, posture may be quite adequate 

 to produce the neck reflex movement, but may be excessive. 

 In the vast majority of rats posturing is totally inadequate, and 

 the neck reflex cannot be produced. When posture is excessive 

 contracture of the body musculature is sometimes disproportion- 

 ate in extent and complexity to produce the neck reflex, for the 

 latch is sent out of the notch with great vigor when this move- 

 ment with the raising of the body takes place. In some cases, 

 before the neck reflex can be prpduced, successive attainments of 

 postures are required, one succeeding the other at shorter or at 

 longer intervals. Often it occurs that two neck reflex movements, 

 or two pushes on the latch and two posturings of the body, one 

 immediately followed by the other are made. In such cases 



