SIZE AND MORPHOLOGY OF BACTERIOPHAGES 



39 



of these phages during the action of oxidizing agents (Figure 3) . 

 WilUams and Fraser (1956) described degradation products 

 produced by freezing and thawing. Both groups reached es- 

 sentially similar conclusions about the structure of the phage 

 tail, which may be described as follows. The tail is composed 

 of a rigid central core or pin running the full length, and an 

 outer tubular sheath. The sheath itself is composed of two 



Figure 3. Left, phage T2, purified prepai ales. X31,- 



500. Unpublished. Right, T2 particles treated with hydrogen peroxide 

 showing alteration of tail structure. X 32,500. Reproduced from E. Kellen- 

 berger and W. Arber, 1955, Z. Naturforsch., 10b, 698, with permission. 



parts. The half proximal to the head of the particle retains its 

 integrity under the influences mentioned, and is occasionally 

 obtained in detached form, when its hollow structure becomes 

 evident. The distal half of the tail sheath is readily removed, 

 and yields long slender fibrils, probably four per phage particle, 

 in the process. These fibrils may be coiled about the tail pin, 

 or may already exist partly as free ends, in the natural state. 

 The central pin often shows a knob at one end, to which remnants 

 of fibrils may or may not be adhering. Isolated pins were ob- 



