private void MenuItemAddMascota_Click(object sender, RoutedEventArgs e)
 {
     canvas.Children.Clear();
     AddMascota c = new AddMascota();
     Titulo.Content = "Zona Mascotas. Añadir";
     canvas.Children.Add(new AddMascota());
     canvas.Height = c.Height;
     canvas.Width = c.Width;
 }
        private void MenuItemPacientes_Click(object sender, RoutedEventArgs e)
        {
            canvas.Children.Clear();
            AddMascota c = new AddMascota();

            Titulo.Content = "Mantenimiento Pacientes";
            canvas.Children.Add(new AddMascota());
            canvas.Height = c.Height;
            canvas.Width  = c.Width;
        }