基类的析构函数不加virtual引起的异常

#include <iostream>
using namespace std;

class Animal{
public:
	static int number;
    virtual void printCount()=0;
    Animal(){
        ++Animal::number;
    }
    virtual ~Animal(){    	//错误点
        --Animal::number;
    }
};

class Dog:public Animal{
	
public:
	static int number;
    Dog(){
        ++Dog::number;
    }
    void printCount(){
        cout<< Dog::number<<endl;
    }
    ~Dog(){
        --Dog::number;
    }
};

class Cat:public Animal{
	
public:
	static int number;
    Cat(){
        ++Cat::number;
    }
    void printCount(){
        cout<< Cat::number<<endl;
    }
    ~Cat(){
        --Cat::number;
    }
};

void print() {
    	cout <<
    	Animal::number << " animals in the zoo, "  
    	<< Dog::number << " of them are dogs, "    
    	<< Cat::number << " of them are cats"      
    	<< endl;
}


int Animal::number = 0;
int Dog::number = 0; 
int Cat::number = 0;
int main() {
    print();  	// 0 0 0 
    Dog d1, d2; //
    Cat c1;
    print();	//3 2 1		动物 狗 猫 
    Dog* d3 = new Dog();   	//4 3 1 
    Animal* c2 = new Cat;	//5 3 2  	受错误点影响的语句(多态语句) 
    Cat* c3 = new Cat;		//6 3 3
    print();				//6 3 3 
    delete c3;				
    delete c2;				//有问题 	受错误点影响的语句 	
    delete d3;
    print();				// 3 2 2	受错误点影响的语句 

}

错误点
1、不加virtual时程序的输出：

2、加virtual时程序的输出：

3、造成两种不同输出的原因：
参考《Effective C++》条款07：为多态基类声明virtual 析构函数 。