. Adventures with animals and plants. Biology. 10. Biologists Study Animals and Plants Fig. 8 (left) The viodern research ftiicroscope is far different from the siviple in- strument of Leeuwenhoek^s day. (spencer lens co.) Fig. 9 (right) One of Leeii- wenhoek's many micro- scopes. A lens was fastened into the metal plate. The rest of the microscope is the object holder, which, by the use of screws, was used to place the object in proper position. Compare this with the moder7i research micro- scope, (bausch and lomb) dog. The saliva flowed from the dog's mouth just the same and in the same amou
. Adventures with animals and plants. Biology. 10. Biologists Study Animals and Plants Fig. 8 (left) The viodern research ftiicroscope is far different from the siviple in- strument of Leeuwenhoek^s day. (spencer lens co.) Fig. 9 (right) One of Leeii- wenhoek's many micro- scopes. A lens was fastened into the metal plate. The rest of the microscope is the object holder, which, by the use of screws, was used to place the object in proper position. Compare this with the moder7i research micro- scope, (bausch and lomb) dog. The saliva flowed from the dog's mouth just the same and in the same amounts. This experiment was per- formed many times, and with many dif- ferent dogs. Always the sound of the bell made the flow of saliva start. Then Pavlov varied his experiment; in one variation, as he showed the food he touched the dog on its hindquarters instead of ringing a bell; in another variation he showed the food and at the same time showed the dog a paper on which a large circle had been drawn. In each experiment, after enough repe- titions there was a flow of saliva even when the food was withheld. Pavlov showed in this way that not only the normal cause, but also an unusual cause, could lead to the flow of saliva in the dog. The experiments taught scientists something about the way in which animals learn. You will read more about this later in the book. But notice how carefully the stage was set for the experiment. Weeks spent in training the dog; years of study to make possible the delicate operation; skillful construction of the cages and harness; patient watching for results; accurate measurement and recording of the facts day after day; the repetition of the experiment with many dogs — all this was necessary to make successful w^hat may have seemed to you at first to have been a relatively simple job. Biologists study the "; The man who first saw "invisible" or micro- scopic creatures was a Dutchman, Anton van Leeuwenhoek (1632-1723
Size: 1755px × 1424px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherbostondcheath, booksubjectbiology
