200 



No. 1) lias examined the development of the muscular fibres 

 in the diaphragm of the foetus. He finds than these are 

 among the earliest muscular fibres developed, and that at 

 birth they have a higher development that the muscular 

 elements connected -with animal (as distinguished from 

 organic) life. This he brings into relation with the imme- 

 diate necessity to the infant of the function of respiration. 



E:mbryology. — Schenck (Pfluger's 'Archiv/ Nos. 2 and 

 3, 1870) has observed a remarkable rotatory movement of 

 the embryo of the common frog within its envelopes. The 

 impregnated and growing ovum may be seen with a simple 

 microscope to be continually rotating on an axis, Avhich is 

 perpendicular to the dorsal furrow of the embryo. The 

 motion may be described as opposite to that of the hands of a 

 clock, if the head of the embryo be regarded as the point of 

 the clock-hand ; or, in other words, an observer situated at 

 the tail end, and looking towards the head, will see the latter 

 turn to his left. The motion is incessant, and undergoes no 

 change till the later stages of development, when the per- 

 fectly horizontal position is changed for an inclined one, the 

 tail end being depressed from the preponderating right of the 

 organs developed in it. The time of rotation varies in dif- 

 ferent specimens, but was generally from five to twelve 

 minutes. Schenck believes ciliary motion to be the cause of 

 the rotation, since it is increased by warmth, which also 

 accelerates the movement of cilia, and is altogether stopped 

 by dilute acids, Avhich equally check ciliary motion. With 

 the death of the embryo both ciliary movement and rotation 

 are suspended. 



