1. The method of continuously monitoring an animal to determine whether the animal has experienced a body temperature in excess of a predetermined level comprising: a. providing a reservoir and tube assembly, containing therein a first reactant and a barrier to movement of said first reactant through said tube and outwardly therefrom, said barrier being displaced upon said assembly reaching said predetermined temperature to permit said first reactant to pass outwardly therefrom; b. inserting the tube portion of said assembly through the cheek of said animal from the inside so as to leave at least the reservoir portion of the assembly in the animal''s mouth; and c. joining an indicator tag portion including a cavity containing a second reactant so as to be in fluid communication with the end of said tube projecting outwardly from said animal so that upon said animal attaining a temperature in excess of said predetermined mimimum the barrier means is displaced and said first reactant will enter said cavity portion of said tag and react with second reactant to produce a color change.

2. The method of continuously monitoring an animal to determine whether the animal has experienced a body temperature in excess of a predetermined level comprising: a. providing a tube and reservoir assembly including at the closed end thereof a first reactant material and in the tube portion thereof a barrier material, said barrier material melting at said predetermined temperature, the open end of said tube being joined to and in fluid communication with the interior cavity of an indicator tag, said interior cavity containing a second reactant material; and, b. inserting the tube portion of said assembly through a hide and flesh portion of the animal to position the portioN of said tube containing said barrier material within the animal leaving the indicator tag external to said animal.

5. An implantable telltale for indicating whether an animal has experienced an internal temperature above a predetermined level comprising: a. a temperature sensor portion including a reservoir and tube assembly defining a chamber, the free end of said tube being of a size and shape to constitute a means for insertion of at least a portion of said tube through the hide portion of an animal to define a means for fluid communication between the inside and outside of the said animal; b. a first reactant material within said chamber; c. an external indicator or tag defining a cavity, said tag constructed and arranged to be joined to the free end of said tube so that the cavity is in fluid communication with said tube at said free end, said cavity containing a second reactant material; and d. a fluid first flow barrier means within said tube for separating said first reactant from said indicator tag cavity, said barrier means defining a temperature controlled removable means in said tube that is displaced when said sensor portion that is internal to said animal has exceeded said predetermined limit thereby mixing said first and second reactants to produce a visual change in said indicator tag that the animal''s body temperature has exceeded said predetermined level.

11. The method of continuously monitoring an animal to determine whether the animal has experienced a body temperature in excess of a predetermined level comprising: a. providing a reservoir and tube assembly containing therein a first reactant and a barrier to movement of said reactant through said tube outwardly therefrom, said barrier being displaced upon said assembly reaching said predetermined temperature to permit the reactant to pass outwardly therefrom; Pg,28 b. joining an indicator tag including a cavity containing a second reactant so as to be in fluid communication with the free end of said tube; c. positioning said reservoir within the mouth of said animal adjacent a lip portion and intermediate the incisor and premolar teeth and looping said tube over the lip of said animal so that said tag is on the outer side of said lip opposite said reservoir; and d. providing means for holding said reservoir, tube and tag in fixed relationship to said lip.

12. An implantable telltale for indicating whether an animal has experienced an internal temperature above a predetermined level comprising: a. a temperature sensor portion including a reservoir and tube assembly defining a first chamber with one end of said tube joined to and in fluid communication with said reservoir and extending outwardly therefrom, the reservoir portion of said assembly being of a configuration and size to be at least semi-permanently lodged within said animal''s mouth; b. said chamber being substantially filled with a thermally expanding material including a first reactant material positioned in conjunction with the second end of the tube portion thereof; c. an indicator tag defining a cavity, said indicator tag being joined to the opposite end of said tube from said reservoir to be in fluid communication therewith, said cavity containing a second reactant material; d. means for at least semi-permanently mounting said reservoir portion within the mouth of an animal with the tag portion of said telltale exterior to said animal; and e. a movable flow barrier means within said tube for selectively separating said first reactant material from said indicator tag cavity, said movable means defining a temperature responsive flow control means for the intermixing of said first and second reactants in said tag when the internal temperature in said animal has exceeded a predetermined level to thereby produce intermixing of said first and second reactants within said indicator tag to provide a visual change in said indicator tag signalling that the animal''s body temperature has exceeded said predetermined level.

18. A method of continuously monitoring an animal to determine whether the animal has experienced a body temperature in excess of a predetermined level comprising: a. providing a reservoir, tube and indicator assembly, said reservoir being substantially filled with a thermally expandable material and including a first reactant material in fluid communication with said tube, said indicator tag defining a cavity containing a second reactant substance and said tube having a barrier means therewithin for normally preventing said first and second reactants from mixing, until the temperature of said reservoir has reached a first predetermined level to Expell said first reactant into said tag cavity; b. inserting said reservoir into the mouth portion of the animal; and c. anchoring said reservoir in at least semi-permanent position within said animal''s mouth.