1922J Rees: The Neuromoior Apparatus of Fanimncvium 3-t9 



Micro-Dissection 



It is difficult to demonstrate by the method of micro-disseetion 

 that the fibers in Paramaecium are eondnctile because : 



In the first place, the animal is not highly specialized, as is the 

 case with EupJotes and as the locomotor organelles are smaller, their 

 coordinated movements are harder to see. 



Secondly, the pellicle is exceedingly hard to cut. It gives way 

 under the pressure of the needle point without being severed and 

 returns to its normal position when the pressure is released. Euplotes 

 was found to be much easier to dis.seet because of its greater resistance 

 to the needle. Furthermore, the only fibers clearly visible in the 

 unstained living animal are those of the cytopharynx. 



Partial transsections through the cytopharynx and hence through 

 these fibers were made, partial transsections also being made elsewhere 

 as control experiments. In addition to the above ents, the region of 

 the neuromotor center was cut and othi'rwise injured with the needle 

 point. 



Short, rapidly tapering needles made of pyrex rods were most 

 effective. With a needle of this type, it was found possible to cut 

 animals in two. 



In four cases where it could be positively determined that the 

 cytopharyngeal fibers had been cut, there was seen a marked differ- 

 ence in rate and amplitude of vibration between the membranelles 

 anterior to the cut and posterior to it. The movement of the posterior 

 membranelles was slower and through a smaller amplitude than that 

 of the anterior membranelles. Severe injury, on both sides of the 

 membranelle zone, produced no detectable disturbance so long as the 

 cytopharyngeal fibers remained intact. Transsections elsewhere like- 

 wise had no effect on the action of the membranelles. In one instance, 

 a wide cut, not quite reaching the cj'topharyngeal fibers, was made 

 in the left side of the animal. No effect was detected in the beating 

 of the membranelles except in cases where these fibers were injured. 

 Verworn (1889) records similar experiments with Spirosiomum. 



When animals were isolated in gelatine, it was possible to observe 

 the ciliary vibrations very clearly. In three cases, severe injury to 

 the animal in the region of the neviromotor center caused a pronounced 

 disturbance of ciliary movement. In one case, no less than four 

 distinct groups of cilia were observed, two on each side, each moving 

 independently of the others. Those on one side were vibrating in 



