INTRODUCTION \ \ 



laboratory for teaching physiology in the United States. Ernest Starling 

 (1866-1927) made many contributions to the physiology of circulation 

 and the nature of lymph and with William Bayliss (1866-1924) eluci- 

 dated the hormonal control of the function of the pancreas. 



The Scottish anatomist John Hunter (1728-1793) and the French 

 anatomist Georges Cuvier (1769-1832) were pioneers in the field of com- 

 parative anatoiny, studying the same structure in different animals. 

 Richard Owen (1804-1892) developed the concepts of homology and 

 analogy. Cuvier was one of the first to study the structure of fossils as 

 well as of living animals and is credited with founding the science of 

 paleontology. Cuvier believed strongly in the unchanging nature of 

 species and carried on bitter debates with Lamarck, who in 1809 pro- 

 posed a theory of evolution based on the idea of the inheritance of 

 acquired characters. 



One of the most important and fruitful concepts in biology is the 

 cell theory, which has gradually grown since Robert Hooke first saw, 

 with the newly invented microscope, the dead cell walls in a piece of 

 cork. The French biologist Rene Dutrochet clearly stated in 1824 that 

 "all organic tissues are actually globular cells of exceeding smallness, 

 which appear to be united only by simple adhesive forces; thus all 

 tissues, all animal organs are actually only a cellular tissue variously 

 modified." Dutrochet recognized that growth is the result of the increase 

 in the volume of individual cells and of the addition of new cells. The 

 German botanist M. J. Schleiden and zoologist Theodor Schwann 

 studied many different plant and animal tissues and are generally 

 credited with formulating the cell theory, for they showed that cells are 

 the units of structure in plants and animals, and that organisms are 

 aggregates of cells arranged according to definite laws. The presence of 

 a nucleus within the cell, now recognized as an almost universal feature 

 of cells, was first described by Robert Brown in 1831. 



Zoology, along with the other biological sciences, has expanded at 

 a tremendous rate in the past century, with the establishment of the 

 subsciences of cytology, embryology, genetics, evolution, biochemistry, 

 biophysics, endocrinology and ecology. The discoveries and new tech- 

 niques of chemistry and physics have made possible new approaches to 

 the biological sciences that have attracted the attention of many biolo- 

 gists. So many men have contributed to the growth of zoology in this past 

 century that only a few in each field can be mentioned: Mendel, deVries, 

 Morgan and Bridges in genetics, Darwin, Dobzhansky, W^right and Gold- 

 schmidt in evolution, and Harrison and Spemann in embryology. Many 

 others will be mentioned as these subjects are discussed in detail in the 

 text. 



The establishment and giowth of the marine biological laboratories 

 such as the ones at Naples, \Voods Hole (Mass.), Pacific Grove (Calif.), 

 Friday Harbor (Wash.), and elsewhere have played an important role in 

 fostering research in zoological sciences. There are comparable stations 

 for the study of fresh-water biology, such as the one at Douglas Lake, 

 Michigan. 



