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J. 0. Wakelin Barratt and G. Arnold 
as the spermatid nucleus. Multivacuolate cell masses of the third dass 
present vacuoles of the same size as the preceding or corisiderably smaller. 
Tliey frequently occur in association with other vacuoles which can be 
recognized to be of the preceding types. The difficulty in identifying 
these vacuoles arises from the impossibility of deciding: 1. whether they 
are surrounded completely or only in part by nuclear material; and also 
2. whether they possess a definite cyst wall. When of very small size 
it is difficult to ascertain if they are surrounded by nuclear material. 
In general aspect these cell masses resemble those of types 1 and 2. 
Fat gl ob ul es have been alreadv referred to on p. 264. 
Debris. We now consider the significance of the shreddv material 
containing Sertolian nuclei, which ultimately forms the sole constituent 
of the tubules about thirteen days after the application of X rays of the 
intensity above indicated. This material, which is finely granulär and 
stains with acid dyes, is for the most part arranged in the form of thin 
expansions, irregularly arranged to form a coarse meshwork extending 
between the basement membrane and the centre of the tubule. 
As regards the origin of this material two views are possible ; 1. that 
of Bergonie and Tribondeau, that it represents a pathological increase 
of what they regard as the normal syncytium,in which the cells of Sertoli 
are conceived to be connected by more or less flat expansions of their 
cytoplasm; 2. that the shreddy material is derived from the breaking 
up of some or all of the varieties of seminal cells, in particular from the 
remains of cytoplasm and of tails of spermatozoa. The appearance of 
sections from the 4th day onwards appeared to indicate that spermatozoal 
tails take part in the formation of this shreddy material. 
Changes in the cells of the testis, resulting from the action of X rays, 
considered from the physiological standpoint. 
Up to the present attention has been directed solely to the structural 
changes occurring in cells of the testis following upon exposure to X rays. 
This article would however be incomplete without some reference to 
the significance of these changes in respect of disturbance of cell function. 
At the outset we are met with the limitation that the study of func- 
tional disturbance is possible only in regard to such functions as are 
already known and that in the case of the testis the data available con- 
cerning the life history of individual cell types is scantv, being based 
almost exclusively upon morphological studies. Although therefore the 
investigation, in seminal cells, of functional disturbances following upon 
