3o6 SCIENCE PROGRESS 



time when the parathyroids attain their functional condition. Since tetany 

 can only be produced by thymus feeding in larvae, of which the parathyroids 

 are still rudimentary, Uhlenhuth advances the suggestion that there is a 

 reciprocal relation between the parathyroids and thymus activities : that 

 the former absorb a tetany toxin manufactured by the latter. This would 

 explain the tetanic consequences of parathyroid removal in Mammals ; but 

 the considerations adduced are not as yet adequate. 



Several workers studying Amphibian metamorphosis have supplied minor 

 data dealing with the interrelationship of the endocrine organs. Both 

 hyperpituitarism (Hoskins) and hypertrophy of the parathyroids (Allen) 

 appear to result from thyroidectomy of the larva. One further contribution 

 merits reference in conclusion, that of McCurd and F. Allen, who studied 

 the effect of feeding with pineal gland on the metamorphosis of tadpoles. 

 They supply evidence that the administration of the gland or its extract 

 is accompanied by striking temporary changes in coloration by influencing 

 the melanophores to contract. There is reason to believe that the reaction 

 of the melanophores is partly under the control of stimuli received by the 

 organs of vision ; and bearing in mind the archaic function of the pineal as 

 an eye structure, as also the close connection between the physiological 

 effects of the suprarenal cortex and medulla respectively on the organs in 

 association with which they arise in autogeny, it will be exceedingly inter- 

 esting if this result is confirmed by subsequent work. 



VERIFIABLE KITOWLEDGE ^ (George Shann) 



The ultimate function of verifiable knowledge is to afford guidance in 

 action ; for which end forecasts of the future must be framed on the basis 

 of knowledge drawn from experience of the past. Such forecasts can be 

 made only on the supposition that certain sequences of change which have 

 occurred previously will recur again in the same order as before. 



It is possible to make forecasts about the course of a sequence even 

 when its elements are looked upon as isolated events, without other mental 

 association than the remembrance that they have occurred in a certain 

 order. In the present day, however, such empirical knowledge is felt to be 

 insufficient, and forecasts are hardly considered to be more than probabilities 

 until the sequences from which they are drawn have been hypothetically 

 arranged in a continuous series, or process. Moreover, a prime desideratum 

 of any such mental arrangement is that it should resemble other processes 

 already imagined to be the connections underlying more familiar series of 

 changes, and hence regarded as known processes. When these conditions 

 are fulfilled, forecasts can be made that, if the newly observed sequence 

 does, throughout its course, follow the lines of the known process, then cer- 

 tain events, not hitherto associated with the sequence, may be expected. 

 The verification of a new hypothesis depends upon the success or failure 

 of such forecasts. 



Among all processes known to us, the most familiar are change of place 

 (motion) and change of motion (acceleration). Sequences of change which 

 can be satisfactorily arranged in terms of these are held to be thoroughly 

 understood ; not because one series is more intelligible than another, but 

 because the analogous series are such as are frequently met with and can 

 be continuously observed, so that very accurate forecasts can be drawn 

 from them. The successive appearances of the planets have been compared 

 with the motion of a heavy body toward the earth, and are therefore said to 

 be explained, although there is no explaining of this latter motion. 



So far as verifiable knowledge has been systematised, it consists entirely 



1 A short paper on the subject appeared in the April number of this 

 magazine. 



