PHOSPHATASES OF NUCLEI OF OTHER CELLS 57 



and that by far the greater part of this is distributed in bands 

 on the chromosomes. It is difficult, however, to study the detail 

 of the arrangement of the bands in the sectioned material since 

 the nuclei are so packed by the chromosomes. When the material 

 is prepared by the standard procedure of the cytologist, i.e., 

 squashing in 45 percent acetic acid, the phosphatase activity is 

 completely destroyed by the acetic acid. If, on the other hand, 

 the nuclei are fixed by fixatives which have comparatively little 

 action on alkaline phosphatase, such as 80 percent alcohol or 

 aqueous formaldehyde, the nuclei take on a rubbery consistency 

 and cannot be squashed. Thus it appears that fixatives which 

 will give a cytologically satisfactory specimen destroy the enzyme, 

 and fixatives which do not destroy the enzyme do not give a sat- 

 isfactory cytological preparation. It was, therefore, necessary 

 to compromise between the irreconcilable ideals of good fixation 

 and retention of phosphatase activity by using various concen- 

 trations of acetic acid for the preparation of squashes. The best 

 results obtained so far were with squashes prepared in 3.4 per- 

 cent acetic acid. The procedure of squashing was carried out 

 as rapidly as possible, and immediately after squashing the 

 cover slips were removed under 95 percent alcohol. After the 

 cover slip was removed, the material was left in 95 percent 

 alcohol for at least 30 minutes. Under these conditions most 

 of the material remained on the cover slip, and most of the 

 material was also either cytologically poor or had its alkaline 

 phosphatase destroyed. In occasional specimens, however, 

 moderately well-fixed chromosomes were observed which had 

 a high phosphatase activity. An example of this is shown in 

 Figs. A and B of Plate IX. Catcheside and Danielli found 

 that in the X chromosome it appeared that the type of distri- 

 bution of phosphatase was identical with that of the Feulgen- 

 positive material. The intensity of the phosphatase reaction 

 in the different bands did not appear to follow the intensity 

 of the Feulgen reaction in the same bands. 



The parallelism between the distribution of phosphatase and 

 of what is presumed to be deoxypentose nucleic acid in the 

 known sites of genes has naturally led to the suggestion that 

 both of these substances may be integral parts of genes. An ex- 

 tension of this contention has been the suggestion that a gene 

 may be a specific array of enzyme molecules, whose synthetic 



