Final answer:
Veterinary clinics do not typically carry Schedule I controlled substances, as these have a high abuse potential, no accepted medical use, and unsafe profiles under medical supervision, contrasting the need for legitimate, accepted medical treatments in veterinary practice.
Step-by-step explanation:
The class of controlled substances that will NOT typically be found in a veterinary clinic is Schedule I drugs, as defined by the Controlled Substances Act. Schedule I drugs are classified as substances that have a high potential for abuse, no currently accepted medical use in treatment in the United States, and a lack of accepted safety for use under medical supervision. Since veterinarians require legitimate and accepted medical substances to treat animals, they would not have these types of drugs, such as heroin, LSD, and marijuana (federal level, as some states have marijuana classified differently).