Cleland • Cytology: the Study of the Cell 



237 



amazing fact that through all this di- 

 versity there runs a unity of structure 

 and function which is equally impres- 

 sive, and most of this unity reveals itself 

 at the cellular level. It is a striking fact 

 that practically all organisms, plant or 

 animal, follow the same laws of hered- 

 ity, based upon the presence of genes 

 carried in chromosomes. Tliese chro- 

 mosomes divide and are transmitted, 

 when cells divide, to the daughter cells 

 by the same process of mitosis, and are 

 parcelled out to the individual repro- 

 ductive cells by the same mechanism 

 of meiosis. The deviations have in- 

 volved relatively unessential aspects; 

 the essential features of living proto- 

 plasm have been retained by all or- 

 ganisms—otherwise they would not 

 have been able to survive. 



This fact has very important prac- 

 tical applications. Cells have the same 

 fundamental attributes, whether they 

 belong to bacteria, the higher plants, 

 or animals. An agent or condition 

 which effects the functioning of one 

 kind of cell is likely to have similar ef- 

 fects on other cells. Many of our most 

 pressing biological problems involve 

 the cell and the behavior of proto- 

 plasm. Cancer, for instance, is a condi- 



tion in which cells have lost the in- 

 hibitors which retard and control 

 growth and cell division. The brakes 

 have been released and the processes 

 of growth and multiplication are un- 

 restrained. The solution of the cancer 

 problem will not be achieved by at- 

 tempts to cure cancer, nor will it neces- 

 sarily come by the study of human 

 tissues, since cancers are found in 

 many other organisms, even in plants. 

 It will not be found until we know 

 what makes cells grow and multiply, 

 what controls and regulates these proc- 

 esses, what substances are capable of 

 throwing a monkey-wrench into the 

 regulatory machiner\', and what part 

 of the machinery they effect. 



From this brief discusion it is evi- 

 dent that cytology deals with the most 

 fundamental properties of living be- 

 ings—how the living material is or- 

 ganized and constructed, how it carries 

 on its multitudinous processes, how it 

 is governed, how it reproduces and 

 transmits to successive generations the 

 powers which it possesses. Tlie answer 

 to all the basic riddles of living nature, 

 so far as they are capable of solution, 

 are to be found in the cell, the happy 

 hunting ground of the cytologist. 



QUESTIONS 



1 Whv is cvtoloev closely allied to the 5. What is plastid or cytoplasmic inheri- 

 search for the nature of are? 



2. What is one disadvantage of staining 

 cells when one is studying protoplasm? 



3. How did Sutton's work verify the find- 

 ings of Mendel? 



4. Describe the Watson-Crick model of 

 a chromosome core. 



tance and of what significance is it? 



6. What was Sonneborns' work on cyto- 

 plasmic inheritance? 



7. How can chromosomes play a part in 

 deciding relationships between organ- 

 isms? 



8. How does Dr. Cleland think the can- 

 cer problem will be solved? 



