FIELD J 



Columns 37, 38, 39, 



40, 41, and 42 



For this reason, it has been unnecessary to use as much IBM space for as large a number of families, 

 genera, and species in Field J as is necessary in Field E. 



When an organism is used as a host in a chemical test, there is introduced an experimental 

 factor that is frequently of critical importance, the relationship between the parasite and its host. 

 For scientific control in a test, it is important that a living host be as carefully selected and stand- 

 ardized as a non-living host, whenever possible. To achieve maximum control, it is frequently not 

 only a particular species that is selected as the parasite's host during the test, but a carefully 

 selected, distinct strain of that species. Within a single species may be several strains which per- 

 form with great dissimilarity as hosts to a given parasite species. Not only may the interrelationships 

 between parasite and the host vary according to the strain of the host into which the parasite is inoc- 

 ulated, but the response of the parasite to chemical treatment may vary with the host strain and the 

 responses of different host strains to the test compound may vary. For this reason, Field J symbols 

 have been endowed with strain (variety or breed) designations, as described above. 



General Use 



Field J is the area for coding the host of a test organism, when the test organism is in or on 

 such a host. This host may be a livin g organism or it may be a non-living environment such as a 

 specific culture medium, soil, stored food (flour and cereal, e. g. ), water, etc. , in or on which the 

 test organism is resident when the test compound is applied. 



A pathology coded in Field E, whether it is infectious (caused by a pathogenic test organism) 

 or non-infectious, is accompanied by an entry in Field J describing the host of the pathogen or pathol- 

 ogy. Likewise, a tumor coded in Field E is accompanied by an entry in Field J describing the living 

 (or, occasionally, non-living) host of the tumor. 



The host represents an important factor of chemical-biological tests, interposed as it most 

 frequently is between the test compound and the object of the treatment in Field E (i. e. , the test 

 organism, pathology, or tumor). A test compound, administered as an experimental therapeutic is 

 applied at a selected (and presumably optimal) site of the host which means that it is often applied 

 only indirectly to the infecting organism, site of pathology, or tumor. Frequently, little is known 

 about the details of the host's metabolic handling and rate or path of disposition of the chemical (i. e. , 

 the host's response to the treatment). Although this observation is made with living hosts particularly 

 in mind, certain non-living host materials may represent unknown factors relative to the dilution/ 

 concentration/alteration of the test compound. Therefore, when a host is involved, the outcome of a 

 test--i. e. , the therapeutic evaluation of the test compound- -must always be interpreted by regarding 

 the host as an agent which possibly acts to dilute, concentrate, or chemically alter the test compound. 

 Division 8, of the following section, explains how this is related to coding procedure. 



Specific Directions and Explanations 



1. An animal or plant PART, excised and maintained in a LIVING CONDITION, as a host; the 

 bath or nutrient solution needed to maintain the excised part 



Occasionally, for convenience in testing, a test organism is in or on an excised part of a host 

 organism rather than in or on the intact host, the excised part being maintained in a living condition or 

 so little altered by excision that its performance as a host is thereby representative of the condition in 

 the intact, living host, in contrast to organs or tissues in which the protoplasmic contents are altered 

 by actual death. (Examples of these "excised living" hosts are organ slices, tissue slices, tissue 

 breis, or excised organs such as the liver, leaves, or fruits. ) Since the results of such tests can 

 reasonably be projected to the intact living organism as a host, Field J is coded with the symbol for 

 the organism and Field L is coded with Symbol R (or Symbol T, as described below) to indicate that it 

 was only a representative part of the host that was actually used in the test. The excised organ or 

 tissue is coded in Field H-l or I. (See also Division 4, below. ) 



69 



